ARM: 7890/1: v7-M: drop using mach/entry-macro.S

The only v7-M platform only has some unused stubs in its
mach/entry-macro.S file. So don't include it which allows efm32 to drop
the file.

Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>