Add macro to check whether the CPU implements an EL

Replace all instances of checks with the new macro.

Change-Id: I0eec39b9376475a1a9707a3115de9d36f88f8a2a
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/include/lib/aarch64/arch.h b/include/lib/aarch64/arch.h
index ef7241d..834434e 100644
--- a/include/lib/aarch64/arch.h
+++ b/include/lib/aarch64/arch.h
@@ -134,6 +134,10 @@
 #define ID_AA64PFR0_EL3_SHIFT	12
 #define ID_AA64PFR0_ELX_MASK	0xf
 
+#define EL_IMPL_NONE		0
+#define EL_IMPL_A64ONLY		1
+#define EL_IMPL_A64_A32		2
+
 #define ID_AA64PFR0_GIC_SHIFT	24
 #define ID_AA64PFR0_GIC_WIDTH	4
 #define ID_AA64PFR0_GIC_MASK	((1 << ID_AA64PFR0_GIC_WIDTH) - 1)