Use devm_request_and_ioremap instead of request_mem_region + devm_ioremap.

This also fixes the following compile error introduced in commit b2ca7f4d
("drivers/video/jz4740_fb.c: use devm_ functions"):

drivers/video/jz4740_fb.c: In function 'jzfb_probe':
	drivers/video/jz4740_fb.c:676:2: error: implicit declaration of function 'devm_ioremap'
	drivers/video/jz4740_fb.c:676:13: warning: assignment makes pointer from integer without a cast
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>