move -ffixed-P5 to blackfin_config.mk and drop unused -D__BLACKFIN__

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

blackfin_config.mk

@@ -21,4 +21,5 @@
 # MA 02111-1307 USA
 #
 
-PLATFORM_CPPFLAGS += -DCONFIG_BLACKFIN -D__BLACKFIN__
+PLATFORM_RELFLAGS += -ffixed-P5
+PLATFORM_CPPFLAGS += -DCONFIG_BLACKFIN

cpu/bf533/config.mk

@@ -24,4 +24,4 @@
 # MA 02110-1301 USA
 #
 
-PLATFORM_RELFLAGS += -mcpu=bf533 -ffixed-P5
+PLATFORM_RELFLAGS += -mcpu=bf533

cpu/bf537/config.mk

@@ -24,4 +24,4 @@
 # MA 02110-1301 USA
 #
 
-PLATFORM_RELFLAGS += -mcpu=bf537 -ffixed-P5
+PLATFORM_RELFLAGS += -mcpu=bf537

cpu/bf561/config.mk

@@ -24,4 +24,4 @@
 # MA 02110-1301 USA
 #
 
-PLATFORM_RELFLAGS += -mcpu=bf561 -ffixed-P5
+PLATFORM_RELFLAGS += -mcpu=bf561