RDMA/bnxt_re: Fix the sideband buffer size handling for FW commands

bnxt_qplib_rcfw_alloc_sbuf allocates 24 bytes and it is better to fit
on stack variables. This way we can avoid unwanted kmalloc call.
Call dma_alloc_coherent directly instead of wrapper
bnxt_qplib_rcfw_alloc_sbuf.

Also, FW expects the side buffer  needs to be aligned to
BNXT_QPLIB_CMDQE_UNITS(16B). So align the size to have the
extra padding bytes.

Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Hongguang Gao <hongguang.gao@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Link: https://lore.kernel.org/r/1691052326-32143-4-git-send-email-selvin.xavier@broadcom.com


Signed-off-by: Leon Romanovsky <leon@kernel.org>