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/plat/qemu/qemu_bl2_setup.c b/plat/qemu/qemu_bl2_setup.c
index 738d671..6c59974 100644
--- a/plat/qemu/qemu_bl2_setup.c
+++ b/plat/qemu/qemu_bl2_setup.c
@@ -226,15 +226,11 @@
  ******************************************************************************/
 static uint32_t qemu_get_spsr_for_bl33_entry(void)
 {
-	unsigned long el_status;
 	unsigned int mode;
 	uint32_t spsr;
 
 	/* Figure out what mode we enter the non-secure world in */
-	el_status = read_id_aa64pfr0_el1() >> ID_AA64PFR0_EL2_SHIFT;
-	el_status &= ID_AA64PFR0_ELX_MASK;
-
-	mode = (el_status) ? MODE_EL2 : MODE_EL1;
+	mode = EL_IMPLEMENTED(2) ? MODE_EL2 : MODE_EL1;
 
 	/*
 	 * TODO: Consider the possibility of specifying the SPSR in