wifi: rtlwifi: rtl8192cu: using calculate_bit_shift()

Using calculate_bit_shift() to replace _rtl92c_phy_calculate_bit_shift().
And fix an undefined bitwise shift behavior problem.

Fixes: f0a39ae7 ("rtlwifi: rtl8192cu: Add routine phy")
Signed-off-by: Su Hui <suhui@nfschina.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20231219065739.1895666-6-suhui@nfschina.com