arm: Add v7_invalidate_l1 to cache-v7.S

mach-socfpga is another platform that needs to use
v7_invalidate_l1 to bringup additional cores. There was a comment that
the ideal place for v7_invalidate_l1 should be in arm/mm/cache-v7.S

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Pavel Machek <pavel@denx.de>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Pavel Machek <pavel@denx.de>
Tested-by: Stephen Warren <swarren@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Olof Johansson <olof@lixom.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Magnus Damm <magnus.damm@gmail.com>
Signed-off-by: Olof Johansson <olof@lixom.net>