ray_cs: Check ioremap return value

ray_cs: Check ioremap return value

As the possible failure of the ioremap(), the 'local->sram' and other
two could be NULL.
Therefore it should be better to check it in order to avoid the later
dev_dbg.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20211230022926.1846757-1-jiasheng@iscas.ac.cn