cnss: using bmi target info from wlan to determine firmware files

Currently we are reading ROME revision id from pci config space and
deciding firmware files based on that. This is not portable across
different buses. Instead, we need to use the revision id read by qcacld
WLAN driver(BMI) to decide firmware files for ROME. This change amends
cnss_get_fw_files API to receive target info and return firmware file
names based on that.

CRs-Fixed: 669587
Change-Id: Ic6ea327737a4ab428020f0ee5414a144a45f21ba
Signed-off-by: Mohit Khanna <mkhannaqca@codeaurora.org>