bcma: add support for 1 and 2 byte extended config space access

The sanity checks allow 1 and 2 byte reads/writes of the extended
PCI config space to proceed; however, the code only supports 4
byte reads/writes.  This patch adds support for 1 and 2 byte
reads/writes of the extended PCI config space.

Signed-off-by: Nathan Hintz <nlhintz@hotmail.com>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>