serial: pch_uart: revert Kconfig for non-DMA mode

PCH_DMA is not always enabled when a user uses PCH_UART.
Since overhead of DMA is not small, in case of low frequent
communication, without DMA is better.
Thus, "select PCH_DMA" and DMADEVICES are unnecessary

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>