ARM: pxa/lubbock: remove lubbock_set_misc_wr() from global view

There are now no users of lubbock_set_misc_wr() outside lubbock.c, so
make this function static.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>