atmel_lcdfb.c: fix printk() type mismatch

This patch fixes a type mismatch when calling dev_info() in the
atmel_lcdfb.c driver.

Signed-off-by: Claudio Scordino <claudio@evidence.eu.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>