mmc: dw_mmc: Handle return value from bounce_buffer_start()

mmc: dw_mmc: Handle return value from bounce_buffer_start()

The bounce_buffer_start() can return -ENOMEM in case memory allocation
failed. However, in that case, the bounce buffer address is the same as
the possibly unaligned input address, and the cache maintenance operations
were not applied to this address. This could cause subtle problems. Add
handling for the bounce_buffer_start() return value to prevent such a
problem from happening.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Simon Glass <sjg@chromium.org>