wifi: rtw89: 8851b: rfk: extend DPK path_ok type to u8

Originally the type of path_ok is bool to denote that DPK is ready on
certain path and can be enabled. For RTL8851B, hardware design can support
more than one calibration set, so use type u8 instead to record the
hardware set in current use.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250627035201.16416-2-pkshih@realtek.com