[ARM] pxa: fix tosa.c build error

Work around:
arch/arm/mach-pxa/tosa.c: In function `tosa_poweroff':
arch/arm/mach-pxa/tosa.c:470: error: `GPIO_OUT' undeclared (first use in this function)
arch/arm/mach-pxa/tosa.c:470: error: (Each undeclared identifier is reported only once
arch/arm/mach-pxa/tosa.c:470: error: for each function it appears in.)

The proper fix exists in the PXA branch of my kernel git tree, which
will be pushed during the next merge window.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>