wifi: ath11k: Flush the posted write after writing to PCIE_SOC_GLOBAL_RESET

wifi: ath11k: Flush the posted write after writing to PCIE_SOC_GLOBAL_RESET

ath11k_pci_soc_global_reset() tries to reset the device by writing to the
PCIE_SOC_GLOBAL_RESET register. But it doesn't do a read-back to ensure
that the write gets flushed to the device before the delay.

This may lead to the delay on the host to be insufficient, if the posted
write doesn't reach the device before the delay.

So add a read-back after writing to the PCIE_SOC_GLOBAL_RESET register and
before the delay.

Compile tested only.

Fixes: f3c603d412b3 ("ath11k: reset MHI during power down and power up")
Reported-by: Alex Williamson <alex@shazbot.org>
Closes: https://lore.kernel.org/linux-pci/20260622160822.09350246@shazbot.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Reviewed-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Reviewed-by: Raj Kumar Bhagat <raj.bhagat@oss.qualcomm.com>
Link: https://patch.msgid.link/20260623141649.41087-1-manivannan.sadhasivam@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>