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>
diff --git a/arch/arm/cpu/pxa/config.mk b/arch/arm/cpu/pxa/config.mk
index 0bbe295..ea55859 100644
--- a/arch/arm/cpu/pxa/config.mk
+++ b/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