ath11k: don't use defines for hw specific firmware directories

The downside of using defines in struct ath11k_hw_params.fw.dir is that it's
easy to get it wrong as the full path is not visible. So drop the use of
defines and instead create the patch runtime using a static inline function
ath11k_core_create_firmware_path(). Hopefully this reduces the chances of using
incorrect firmware path.

No functional changes. Compile tested only.

Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1592316055-24958-8-git-send-email-kvalo@codeaurora.org