[ARM] pxa: introduce cpu_is_pxa26x()

PXA26x (PXA261/262) is actually a PXA250 with stacked Intel(R)
StartaFlash. And this can be decided by bit 3 (PKG_TYPE) of
BOOT_DEF register.

Due to this extra I/O register access, make cpu_is_pxa26x() a
public function instead of a macro.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-pxa/include/mach/hardware.h

@@ -202,6 +202,8 @@
 		__cpu_is_pxa25x(read_cpuid_id());	\
 	})
 
+extern int cpu_is_pxa26x(void);
+
 #define cpu_is_pxa27x()					\
 	({						\
 		__cpu_is_pxa27x(read_cpuid_id());	\