ppc: remove -ffixed-r14 gcc option.

This is no loger needed, free up r14 for general usage.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
diff --git a/cpu/74xx_7xx/config.mk b/cpu/74xx_7xx/config.mk
index d589210..df1f6ac 100644
--- a/cpu/74xx_7xx/config.mk
+++ b/cpu/74xx_7xx/config.mk
@@ -21,6 +21,6 @@
 # MA 02111-1307 USA
 #
 
-PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
+PLATFORM_RELFLAGS += -fPIC -meabi
 
 PLATFORM_CPPFLAGS += -DCONFIG_74xx_7xx -ffixed-r2 -mstring