mtd: gpmi: change pr_err to dev_err

There are pr_err and dev_err in the gpmi driver now.
It makes people confused.

This patch changes all the pr_err to dev_err except the one
in the gpmi_reset_block(). We also remove the unnecessary
print for OOM message.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>