cnss2: Fix mhi compilation errors

This commit fixes programming errors in the driver.

1. Define cnss_mhi_link_status() before using it
2. Define cnss_pci_check_mhi_state_bit() before using it
3. Define cnss_pci_set_mhi_state_bit() before using it
4. Remove static keyword from cnss_pci_force_fw_assert_hdlr()
   definition as it has been already taken care in header file
   pci.h

Change-Id: I2d4e27eac287489f7e563910f9bc1485524a23f0
Signed-off-by: Rishi Gupta <rishgupt@codeaurora.org>