ARM: OMAP AM3517/05: hwmod data: block WFI when EMAC active

According to Mark Greer, on OMAP AM3517/3505 chips, the EMAC is unable
to wake the ARM up from WFI:

    http://www.spinics.net/lists/arm-kernel/msg174734.html

Further troubleshooting was unable to narrow the problem down.  So we
don't have much choice other than to block WFI when the EMAC is active
with the HWMOD_BLOCK_WFI flag.

Based on Mark's original patch.  We're removing the omap_device-based
pm_lats code, so a different approach was needed.

This third version contains some corrections thanks to Mark's review.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Mark A. Greer <mgreer@animalcreek.com>
Acked-by: Mark A. Greer <mgreer@animalcreek.com>