vmbase: entry.S: Reset if relocated

As vmbase-based baremetal code isn't position-independent, refuse to
keep booting if the image wasn't loaded where we intended it to be.

Test: atest MicrodroidTestApp
Change-Id: I9980d82cc43e66fd368812da0e4197bd88dd2b12
diff --git a/vmbase/entry.S b/vmbase/entry.S
index e1d2c98..5f0a2ce 100644
--- a/vmbase/entry.S
+++ b/vmbase/entry.S
@@ -85,6 +85,16 @@
 	adr x30, vector_table_panic
 	msr vbar_el1, x30
 
+	/*
+	 * Our load address is set by the host so validate it before proceeding.
+	 */
+	adr x30, entry
+	mov_i x29, entry
+	cmp x29, x30
+	b.eq 1f
+	reset_or_hang
+1:
+
 	adrp x30, idmap
 	msr ttbr0_el1, x30