bus: mhi: host: pci_generic: Switch to async power up to avoid boot delays

bus: mhi: host: pci_generic: Switch to async power up to avoid boot delays

Some modem devices can take significant time (up to 20 secs for sdx75) to
enter mission mode during initialization. Currently, mhi_sync_power_up()
waits for this entire process to complete, blocking other driver probes
and delaying system boot.

Switch to mhi_async_power_up() so probe can return immediately while MHI
initialization continues in the background. This eliminates lengthy boot
delays and allows other drivers to probe in parallel, improving overall
system boot performance.

Fixes: 5571519009d0 ("bus: mhi: host: pci_generic: Add SDX75 based modem support")
Signed-off-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260303-b4-async_power_on-v2-1-d3db81eb457d@oss.qualcomm.com