tests/tcg: fix semihosting SYS_EXIT for aarch64 in boot.S

We don't expect to hit exceptions in our testing so currently all the
vectors report an un-expected exception and then attempt to exit.
However for aarch64 we should always use the extended information
block as we do in _exit. Rather than duplicate the code on the error
handler just branch to the _exit handler with a failing status code.

Signed-off-by: Alex Bennée <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-Id: <[email protected]>

Author: stsquad

tests/tcg/aarch64/system/boot.S

@@ -73,9 +73,8 @@ lower_a32_serror:
 	mov	x0, SYS_WRITE0
 	adr	x1, .error
 	semihosting_call
-	mov	x0, SYS_EXIT
-	mov	x1, 1
-	semihosting_call
+	mov	x0, 1 /* EXIT_FAILURE */
+	bl 	_exit
 	/* never returns */
 
 	.section .rodata