Read the frequency just set and fix typos

Since ampctl is using the dummy driver, the status is reset at
every run and it can't read the value set during the previous run.

tests/amptest.sh

@@ -11,12 +11,11 @@
 ./ampctl l PWRFORWARD l PWRFORWARD
 ./ampctl l PWRREFLECTED l PWRREFLECTED
 ./ampctl l PWRPEAK l PWRPEAK
-# Powerstat 0=Off, 1=On, 2=Standbyd, 4=Operate, 8=Unknown
+# Powerstat 0=Off, 1=On, 2=Standby, 4=Operate, 8=Unknown
 ./ampctl \set_powerstat 0
 ./ampctl \set_powerstat 1
 ./ampctl \set_powerstat 2
 ./ampctl \set_powerstat 4
 ./ampctl \set_powerstat 8
-# Sets/reads tuner frequenchy
-./ampctl F 14074000
-./ampctl f
+# Sets/reads tuner frequency
+./ampctl F 14074000 f