mxser: fix compiler warning when building without CONFIG_PCI

drivers/char/mxser.c:386: warning: 'mxser_get_PCI_conf' declared 'static' but never defined

when building without CONFIG_PCI.

[jesper.juhl@gmail.com: Fix warning: 'CheckIsMoxaMust' defined but not used]
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>