net: cnss: Fix crash when SDIO device is not inserted

Check to see if the host is not NULL before trying to use
it, this avoids a crash when the driver is probed, but the
card is not available. Also remove dependency on ARCH_MSM
since it is not used anymore.

Change-Id: I476a512dd41e0c336b71c96d8dd2972cdadb8732
Signed-off-by: Gustavo Solaira <gustavos@codeaurora.org>