Bluetooth: btmtksdio: refactor btmtksdio_runtime_[suspend|resume]()

Refactor btmtksdio_runtime_[suspend|resume]() to create the common
funcitons btmtksdio_[fw|drv]_pmctrl() shared with btmtksdio_[open|close]()
to avoid the redundant code as well.

This is also a prerequisite patch for the incoming patches.

Co-developed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Mark Chen <mark-yw.chen@mediatek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>