PCI: pciehp: Add HXT quirk for Command Completed errata

The HXT SD4800 PCI controller does not set the Command Completed bit unless
writes to the Slot Command register change "Control" bits.

Add SD4800 to the quirk.

Signed-off-by: Shunyong Yang <shunyong.yang@hxt-semitech.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Joey Zheng <yu.zheng@hxt-semitech.com>