arm: Do not clear LR on exception in SPL

When an exception or interrupt occurs the link register (LR) may
contain the source of the exception, although we do not print the
value it may still be extracted with a debugger. When in SPL we
loop on getting and exception, but use a linking branch, which
over-writes the LR value, use a regular branch instruction here.
Signed-off-by: NAndrew F. Davis <afd@ti.com>

arch/arm/lib/vectors.S

@@ -133,7 +133,7 @@ not_used:
 irq:
 fiq:
 1:
-	bl	1b			/* hang and never return */
+	b	1b			/* hang and never return */
 
 #else	/* !CONFIG_SPL_BUILD */