ath10k: unify warning messages in mac.c

Currently there are different styles used for warning messages, unify them to
look similar. The style basically is:

1) start with a verb (if possible)

2) lower case letters

3) use plain english as much as possible

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: better firmware loading error messages

Let user know the name of the board file if it is not
found, and make it easier to determine the firmware
api being used.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: add otp and firmware boot error messages

If OTP or firmware fails to load properly, print out some
extra info in the kernel logs.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>