mfd: Several MFD drivers should depend on GENERIC_HARDIRQS

commit 5fb4d38b ("mfd: Move WM831x to
generic IRQ") didn't take into account that genirq support depends on
GENERIC_HARDIRQS.

Additionally, 2.6.34-rc1 added:
  - commit 2afa62ea ("mfd: Use genirq in
    88pm860x").
  - commit 760e4518 ("mfd: Convert WM8350 to
    genirq").
  - commit 1f1cf8f9 ("mfd: Update irq handler
    in max8925")

Make all of them depend on GENERIC_HARDIRQS to avoid compile errors on
architectures that don't support genirq yet.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>