ARM: pxa: mark raumfeld init functions as __maybe_unused

The raumfeld.c file contains three similar machine definitions,
each with their own init function. If one or more of them are
disabled, we get compile-time warnings:

arm/mach-pxa/raumfeld.c:1070:123: warning: 'raumfeld_connector_init' defined but not used [-Wunused-function]
arm/mach-pxa/raumfeld.c:1082:123: warning: 'raumfeld_speaker_init' defined but not used [-Wunused-function]

This marks the functions as __maybe_unused to avoid the warnings.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Daniel Mack <daniel@zonque.org>