Remove build option `ASM_ASSERTION`

The build option `ENABLE_ASSERTIONS` should be used instead. That way
both C and ASM assertions can be enabled or disabled together.

All occurrences of `ASM_ASSERTION` in common code and ARM platforms have
been replaced by `ENABLE_ASSERTIONS`.

ASM_ASSERTION has been removed from the user guide.

Change-Id: I51f1991f11b9b7ff83e787c9a3270c274748ec6f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/lib/cpus/aarch32/cpu_helpers.S b/lib/cpus/aarch32/cpu_helpers.S
index dc1b6e6..7606b8e 100644
--- a/lib/cpus/aarch32/cpu_helpers.S
+++ b/lib/cpus/aarch32/cpu_helpers.S
@@ -53,7 +53,7 @@
 	/* Get the matching cpu_ops pointer (clobbers: r0 - r5) */
 	bl	get_cpu_ops_ptr
 
-#if ASM_ASSERTION
+#if ENABLE_ASSERTIONS
 	cmp	r0, #0
 	ASM_ASSERT(ne)
 #endif
@@ -92,7 +92,7 @@
 	pop	{r2, lr}
 
 	ldr	r0, [r0, #CPU_DATA_CPU_OPS_PTR]
-#if ASM_ASSERTION
+#if ENABLE_ASSERTIONS
 	cmp	r0, #0
 	ASM_ASSERT(ne)
 #endif
@@ -118,7 +118,7 @@
 	cmp	r1, #0
 	bne	1f
 	bl	get_cpu_ops_ptr
-#if ASM_ASSERTION
+#if ENABLE_ASSERTIONS
 	cmp	r0, #0
 	ASM_ASSERT(ne)
 #endif