mac: region: RegionCommon: fix implicit double promotion (#1600)

The calculation is done with float variables. However, the floor
function is meant for double variables. floorf should be used instead.

The implicit double promotion leads to a warning/error if compiled with
LLVM.

Signed-off-by: Martin Jäger <martin@libre.solar>

Author: martinjaeger

src/mac/region/RegionCommon.c

@@ -463,7 +463,7 @@ int8_t RegionCommonComputeTxPower( int8_t txPowerIndex, float maxEirp, float ant
 {
     int8_t phyTxPower = 0;
 
-    phyTxPower = ( int8_t )floor( ( maxEirp - ( txPowerIndex * 2U ) ) - antennaGain );
+    phyTxPower = ( int8_t )floorf( ( maxEirp - ( txPowerIndex * 2U ) ) - antennaGain );
 
     return phyTxPower;
 }