mtd: rawnand: brcmnand: Demote non-conformant kernel-doc headers

Fixes the following W=1 kernel build warning(s):

 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1854: warning: Function parameter or member 'host' not described in 'brcmnand_edu_trans'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1854: warning: Function parameter or member 'addr' not described in 'brcmnand_edu_trans'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1854: warning: Function parameter or member 'buf' not described in 'brcmnand_edu_trans'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1854: warning: Function parameter or member 'len' not described in 'brcmnand_edu_trans'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1854: warning: Function parameter or member 'cmd' not described in 'brcmnand_edu_trans'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'host' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'desc' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'addr' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'buf' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'len' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'dma_cmd' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'begin' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'end' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1951: warning: Function parameter or member 'next_desc' not described in 'brcmnand_fill_dma_desc'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1977: warning: Function parameter or member 'host' not described in 'brcmnand_dma_run'
 drivers/mtd/nand/raw/brcmnand/brcmnand.c:1977: warning: Function parameter or member 'desc' not described in 'brcmnand_dma_run'

Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Kamal Dasu <kdasu.kdev@gmail.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: linux-mtd@lists.infradead.org
Cc: bcm-kernel-feedback-list@broadcom.com
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20201109182206.3037326-14-lee.jones@linaro.org