ARM: 7139/1: fix compilation with CONFIG_ARM_ATAG_DTB_COMPAT and large TEXT_OFFSET

If TEXT_OFFSET is too large (e.g. like on MSM) the resulting immediate
argument gets wider than 8 bits.

Noticed by David Brown <davidb@codeaurora.org>

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/boot/compressed/head.S

@@ -269,7 +269,8 @@ restart:	adr	r0, LC0
 		 * of RAM and hope for the best.
 		 */
 		cmp	r0, #1
-		sub	r0, r4, #(TEXT_OFFSET - 0x100)
+		sub	r0, r4, #TEXT_OFFSET
+		add	r0, r0, #0x100
 		mov	r1, r6
 		sub	r2, sp, r6
 		blne	atags_to_fdt