modprobe.d: add setting for redpine rf tx/rx power modes

Setting 0x22 would be "low" power, 0x11 would be "medium" power. 0x00 is the default.
This doesn't change anything but eases testing.
4 jobs for redpine_rf_powersave in 2 minutes and 22 seconds (queued for 1 second)
Status Name Job ID Coverage
  Package
passed package-pureos-byzantium #375977
librem5

00:00:49

passed package-pureos-byzantium:arm64 #375978
librem5:arm64

00:02:20

 
  Test Package
passed autopkgtest-pureos-byzantium-package #375979
librem5

00:00:53

passed lintian-pureos-byzantium-package #375980
librem5

00:00:58