ath11k: create a common function to request all firmware files

To avoid duplicating the logic how the full firmware path is created create a
common function ath11k_core_firmware_request() and convert also qmi.c to use it.

Also remove a useless info print, it's more like a debug message anyway.

No functional changes. Compile tested only.

Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1592316055-24958-7-git-send-email-kvalo@codeaurora.org