cnss2: Remove PCI ioremap wrapper function

Driver should directly call PCI ioremap API, and not customize
it with wrapper function which is only a WAR for QCA6290 chipset
emulation.

Change-Id: Icba3ce0ebbcef94d75a1713f4776524b909e5552
CRs-fixed: 2059087
Signed-off-by: Yue Ma <yuem@codeaurora.org>