ARM: integrator: localize the lm.h header

As we move toward multiplatform support for the Integrator family
we need to localize all <mach/*> headers. This moves the lm.h
header down to the machine folder as it is not used outside it
anyway.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Jonathan Austin <jonathan.austin@arm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>