wifi: rtlwifi: rtl8723{be,ae}: using calculate_bit_shift()

Using calculate_bit_shift() to replace rtl8723_phy_calculate_bit_shift().
And fix an undefined bitwise shift behavior problem.

Signed-off-by: Su Hui <suhui@nfschina.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20231219065739.1895666-12-suhui@nfschina.com