pxa: use -mcpu=xscale compiler option

Pass '-mcpu=xscale' to the compiler instead of march and mtune.  This will cause
gcc to define the __XSCALE__ macro.

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>

arch/arm/cpu/pxa/config.mk

@@ -24,7 +24,7 @@
 
 PLATFORM_RELFLAGS += -fno-common -ffixed-r8 -msoft-float
 
-PLATFORM_CPPFLAGS += -march=armv5te -mtune=xscale
+PLATFORM_CPPFLAGS += -mcpu=xscale
 # =========================================================================
 #
 # Supply options according to compiler version