wifi: mt76: mt7921e: Set memory space enable in PCI_COMMAND if unset

When the BIOS has been configured for Fast Boot, systems with mt7921e
have non-functional wifi.  Turning on Fast boot caused both bus master
enable and memory space enable bits in PCI_COMMAND not to get configured.

The mt7921 driver already sets bus master enable, but explicitly check
and set memory access enable as well to fix this problem.

Tested-by: Anson Tsao <anson.tsao@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Acked-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>