ARM: 8670/1: V7M: Do not corrupt vector table around v7m_invalidate_l1 call

ARM: 8670/1: V7M: Do not corrupt vector table around v7m_invalidate_l1 call

commit 6d80594936914e798b1b54b3bfe4bd68d8418966 upstream.

We save/restore registers around v7m_invalidate_l1 to address pointed
by r12, which is vector table, so the first eight entries are
overwritten with a garbage. We already have stack setup at that stage,
so use it to save/restore register.

Fixes: 6a8146f420be ("ARM: 8609/1: V7M: Add support for the Cortex-M7 processor")
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>