staging: rtl8192e: Remove function rtl92e_is_legal_rf_path

staging: rtl8192e: Remove function rtl92e_is_legal_rf_path

Remove function rtl92e_is_legal_rf_path that will always return 1. Reason
is that the eRFPath is always 0 for RF90_PATH_A or 1 for RF90_PATH_B but
never 2 or 3. In most usage cases this is easy to see but for the
following functions that use rtl92e_is_legal_rf_path it is more
difficult:
rtl92e_set_rf_reg and rtl92e_get_rf_reg are used in:
rtl92e_set_bandwidth (eRFPath only for 0 and 1)
rtl92e_config_rf (eRFPath only for 0 and 1)
_rtl92e_phy_switch_channel_step (eRFPath only for 0 and 1)
_rtl92e_dm_check_tx_power_tracking_thermal (eRFPath only for 0)
rtl92e_check_bb_and_rf is used in:
rtl92e_config_rf (eRFPath only for 0 and 1)
_rtl92e_bb_config_para_file (eRFPath only for 0)
rtl92e_config_rf_path is used in:
rtl92e_config_rf (eRFPath only for 0 and 1)
Remove dead code.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/b801f1f9ff3c58aedab4e3e07b2ec0a816fdf5d9.1678740713.git.philipp.g.hortmann@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>