Apply compile-time check for AArch64-only cores

Some cores support only AArch64 mode. In those cores, only a limited
subset of the AArch32 system registers are implemented. Hence, if TF-A
is supposed to run on AArch64-only cores, it must be compiled with
CTX_INCLUDE_AARCH32_REGS=0.

Currently, the default settings for compiling TF-A are with the AArch32
system registers included. So, if we compile TF-A the default way and
attempt to run it on an AArch64-only core, we only get a runtime panic.

Now a compile-time check has been added to ensure that this flag has the
appropriate value when AArch64-only cores are included in the build.

Change-Id: I298ec550037fafc9347baafb056926d149197d4c
Signed-off-by: John Tsichritzis <john.tsichritzis@arm.com>
diff --git a/lib/cpus/aarch64/neoverse_e1.S b/lib/cpus/aarch64/neoverse_e1.S
index 71e7b51..d840da8 100644
--- a/lib/cpus/aarch64/neoverse_e1.S
+++ b/lib/cpus/aarch64/neoverse_e1.S
@@ -16,6 +16,11 @@
 #error "Neoverse E1 must be compiled with HW_ASSISTED_COHERENCY enabled"
 #endif
 
+/* 64-bit only core */
+#if CTX_INCLUDE_AARCH32_REGS == 1
+#error "Neoverse-E1 supports only AArch64. Compile with CTX_INCLUDE_AARCH32_REGS=0"
+#endif
+
 func neoverse_e1_cpu_pwr_dwn
 	mrs	x0, NEOVERSE_E1_CPUPWRCTLR_EL1
 	orr	x0, x0, #NEOVERSE_E1_CPUPWRCTLR_EL1_CORE_PWRDN_BIT