sdhci: Add support for hosts reporting inverted write-protect state

This patch adds SDHCI_QUIRK_INVERTED_WRITE_PROTECT quirk. When
specified, the sdhci driver will invert WP state.

p.s. Actually, the quirk is more board-specific than
     controller-specific.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>