power: sequencing: pcie-m2: add SERIAL_DEV_BUS dependency

power: sequencing: pcie-m2: add SERIAL_DEV_BUS dependency

The newly added serdev code fails to link when serdev is turned off:

arm-linux-gnueabi-ld: drivers/power/sequencing/pwrseq-pcie-m2.o: in function `pwrseq_pcie_m2_remove_serdev':
pwrseq-pcie-m2.c:(.text+0xc8): undefined reference to `serdev_device_remove'
arm-linux-gnueabi-ld: drivers/power/sequencing/pwrseq-pcie-m2.o: in function `pwrseq_m2_pcie_notify':
pwrseq-pcie-m2.c:(.text+0x69c): undefined reference to `of_find_serdev_controller_by_node'
arm-linux-gnueabi-ld: pwrseq-pcie-m2.c:(.text+0x6f8): undefined reference to `serdev_device_alloc'
arm-linux-gnueabi-ld: pwrseq-pcie-m2.c:(.text+0x724): undefined reference to `serdev_device_add'

Add another Kconfig dependency for this

Fixes: 3f736aecbdc8 ("power: sequencing: pcie-m2: Create serdev device for WCN7850 bluetooth")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20260401191030.948046-1-arnd@kernel.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>