mpfr: Convert to use BBCLASSEXTEND

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

meta/packages/mpfr/mpfr-native_2.3.1.bb

@@ -1,4 +0,0 @@
-require mpfr_${PV}.bb
-inherit native
-DEPENDS = "gmp-native"
-

meta/packages/mpfr/mpfr-nativesdk_2.3.1.bb

@@ -1,4 +0,0 @@
-require mpfr_${PV}.bb
-inherit nativesdk
-DEPENDS = "gmp-nativesdk"
-

meta/packages/mpfr/mpfr_2.3.1.bb

@@ -5,3 +5,5 @@ PR = "r1"
 
 SRC_URI = "http://www.mpfr.org/mpfr-${PV}/mpfr-${PV}.tar.bz2"
 S = "${WORKDIR}/mpfr-${PV}"
+
+BBCLASSEXTEND = "native nativesdk"