PCI: keystone: Use quirk to limit MRRS for K2G

PCI controller in K2G also has a limitation that memory read request
size (MRRS) must not exceed 256 bytes. Use the quirk to limit MRRS
(added for K2HK, K2L and K2E) for K2G as well.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>