RPi: Improve board revision detection (#681)

Revision detection is done at runtime, the configure script has been
simplified to reflect this.

configure

@@ -14,7 +14,6 @@ Help:
 Building options:
     --soc=[BCM2835|BCM2836|AM33XX|A10|A13|A20|H3]
                                 SoC type to be used. [configure autodetected]
-    --platform-type=<TYPE>      Type of platform
     --cpu-flags=<CPUFLAGS>      CPU defining/optimizing flags to be used. [configure autodetected]
     --extra-cflags=<CFLAGS>     Extra C flags passed to C compilation. []
     --extra-cxxflags=<CXXFLAGS> Extra C++ flags passed to C++ compilation. []
@@ -109,7 +108,6 @@ function detect_machine {
     fi
     local soc="unknown"
     local tp="unknown"
-    local rev="unknown"
 
     if [ -z "$cpu" ]; then
         cpu="unknown"
@@ -120,13 +118,12 @@ function detect_machine {
         soc="BCM2835"
         if [[ $machine == "Raspberry"* ]]; then
             tp="RPi"
-            rev=($(detect_rpi_revision))
         fi
         ;;
     BCM2709)
         soc="BCM2836"
         if [[ $machine == "Raspberry"* ]]; then
-            rev=($(detect_rpi_revision))
+            local rev=($(detect_rpi_revision))
             if [[ $rev == "a02082" || $rev == "a22082" ]]; then
                 tp="RPi3"
             else
@@ -187,7 +184,7 @@ function detect_machine {
     *)
         soc="unknown"
     esac
-    echo "${soc} ${tp} ${cpu} ${rev}"
+    echo "${soc} ${tp} ${cpu}"
 }
 
 function gcc_cpu_flags {
@@ -409,12 +406,7 @@ if [ -z "${SOC}" ]; then
     SOC=${info[0]}
     TYPE=${info[1]}
     CPU=${info[2]}
-    REV=${info[3]}
-    echo "[OK] machine detected: SoC=${SOC}, Type=${TYPE}, CPU=${CPU}, REV=${REV}."
-fi
-
-if [ "${PT}" ]; then
-    TYPE=${PT}
+    echo "[OK] machine detected: SoC=${SOC}, Type=${TYPE}, CPU=${CPU}."
 fi
 
 if [ -z "${CPUFLAGS}" ]; then
@@ -425,10 +417,6 @@ if [[ $SOC == "BCM2835" || $SOC == "BCM2836" ]]; then
     CPPFLAGS="-DLINUX_ARCH_RASPBERRYPI $CPPFLAGS"
 fi
 
-if [[ $TYPE == "RPi2" || $TYPE == "RPi3" || $REV == "0010" ]]; then
-    CPPFLAGS="-D__RPI_BPLUS $CPPFLAGS"
-fi
-
 if [[ ${debug} == "enable" ]]; then
     CPPFLAGS="-DMY_DEBUG $CPPFLAGS"
 fi