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been replaced by `ENABLE_ASSERTIONS`.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/common/aarch32/debug.S b/common/aarch32/debug.S
index bafce7c..adb6dc3 100644
--- a/common/aarch32/debug.S
+++ b/common/aarch32/debug.S
@@ -90,7 +90,7 @@
 	no_ret	plat_panic_handler
 endfunc report_exception
 
-#if ASM_ASSERTION
+#if ENABLE_ASSERTIONS
 .section .rodata.assert_str, "aS"
 assert_msg1:
 	.asciz "ASSERT: File "
@@ -155,7 +155,7 @@
 #endif /* LOG_LEVEL >= LOG_LEVEL_INFO */
 	no_ret	plat_panic_handler
 endfunc asm_assert
-#endif
+#endif /* ENABLE_ASSERTIONS */
 
 /*
  * This function prints a string from address in r4