ARM: assabet: fix bogus warning in get_assabet_scr (again)

Russell fixed this bogus warning before in 2f3eca8b "Shut up gcc
warning in assabet.c", but apparently gcc has become smarter (or dumber)
since 2005, and the same warning came up again.

This uses the uninitialized_var() macro to convince gcc that the
variable is actually being initialized. 100 times in fact.

Without this patch, building assabet_defconfig results in:

arch/arm/mach-sa1100/assabet.c: In function 'fixup_assabet':
arch/arm/mach-sa1100/assabet.c:397:6: warning: 'scr' may be used uninitialized in this function [-Wuninitialized]
arch/arm/mach-sa1100/assabet.c:389:16: note: 'scr' was declared here
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-sa1100/assabet.c

@@ -388,7 +388,7 @@ static void __init map_sa1100_gpio_regs( void )
  */
 static void __init get_assabet_scr(void)
 {
-	unsigned long scr, i;
+	unsigned long uninitialized_var(scr), i;
 
 	GPDR |= 0x3fc;			/* Configure GPIO 9:2 as outputs */
 	GPSR = 0x3fc;			/* Write 0xFF to GPIO 9:2 */