ARM: pxa: PXA_ESERIES depends on FB_W100.

As arch/arm/mach-pxa/eseries.c references w100fb_gpio_{read,write}()
directly.

Signed-off-by: Lennert Buytenhek <buytenh@secretlab.ca>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>