wifi: rtw89: regd/acpi: support country CA by BIT(1) in 6 GHz SP conf

ACPI DSM function 7 is used to decide whether 6 GHz Standard Power
(SP) is allowed on given countries. Now, add BIT(1) for country CA.
Besides, for searching country index, replace for-loop with index
getter function.

Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250709065006.32028-2-pkshih@realtek.com