xen/arm32: head: Mark the end of subroutines with ENDPROC

putn() and puts() are two subroutines. Add ENDPROC for the benefits of
static analysis tools and the reader.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/arm32/head.S

@@ -518,6 +518,7 @@ puts:
         moveq pc, lr
         early_uart_transmit r11, r1
         b puts
+ENDPROC(puts)
 
 /*
  * Print a 32-bit number in hex.  Specific to the PL011 UART.
@@ -537,6 +538,7 @@ putn:
         subs  r3, r3, #1
         bne   1b
         mov   pc, lr
+ENDPROC(putn)
 
 hex:    .ascii "0123456789abcdef"
         .align 2