staging: pi433: add dependency to PA0, 1, 2 setting for output power level

When setting output power level called, the power level should be
checked by power amplifier level register and high power option. There
was todo about it. Add some variables for checking power level range.
The values that used for checking high power or minimum power are from
rf69 datasheets. The maximum power level is always same regardless of
mode.

Signed-off-by: Sidong Yang <realwakka@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>