hvmloader: Explicitly revert to text section after declaring bss fields.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

tools/firmware/hvmloader/hvmloader.c

@@ -96,6 +96,7 @@ asm (
     "stack:                          \n"
     "    .skip    0x4000             \n"
     "stack_top:                      \n"
+    "    .text                       \n"
     );
 
 void smp_initialise(void);

tools/firmware/hvmloader/smp.c

@@ -66,6 +66,7 @@ asm (
     "stack:                          \n"
     "    .skip    0x4000             \n"
     "stack_top:                      \n"
+    "    .text                       \n"
     );
 
 /*static*/ void ap_start(void)