wl1271: fix radio and general parameters commands

We were missing the command header in the radio and general parameters
commands.  This was causing them to fail, resulting in problems in the power
levels and other PLT-related commands.

Also reorganized the command functions, moving from wl1271_init.c to
wl1271_cmd.c where it fits better.

Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Reviewed-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>