wifi: rtw89: call power_on ahead before selecting firmware

Driver selects firmware by hardware version, which normally can be read
from registers before selecting firmware. However, certain chips such as
RTL8851B, it needs to read hardware version from efuse while doing
power_on, but do power_on after selecting firmware in current flow.

To resolve this flow problem, move power_on out from
rtw89_mac_partial_init(), and call rtw89_mac_pwr_on() separately at
proper places to have expected flow.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250203072911.47313-2-pkshih@realtek.com