driver, gpio: Add support for MPC 8xx CPU ports

Ports A, C and D are 16 bits ports.
Ports B and E are 32 bits ports.

The "compatible" is used to determine each port type.

This patch was originally written by Charles Frey who's
email address is not valid anymore as he left the company.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: FRANJOU Stephane <stephane.franjou@csgroup.eu>