ath10k: make ath10k_hw_ce_regs const

Make them const as they are not modified in the file referencing
them. They are only stored in the const field 'hw_ce_reg' of an ath10k
structure. Also, make the declarations in the header const.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>