cnss2: Refactor registers dump APIs

cnss_pci_dump_misc_reg() is meant to dump WLAN related registers, so
move dumping MHI registers out of it. Rename cnss_pci_dump_registers()
to cnss_pci_dump_debug_reg() for better understanding and consistency
with other registers dump APIs.

Change-Id: Ibf1e59f34eac78ae1cd375ac13170917f7ea05d3
Signed-off-by: Yue Ma <yuem@codeaurora.org>