mmc: sdhci-iproc: add bcm2835 support

Scott Branden from Broadcom said that the BCM2835 eMMC IP core is
very similar to IPROC and share most of the quirks. So use this driver
instead of separate one.

The sdhci-iproc contains a better workaround for the clock domain
crossing problem which doesn't need any delays. This results in a
better write performance.

Btw we get the rid of the SDHCI_CAPABILITIES hack in the sdhci_readl
function.

Suggested-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Eric Anholt <eric@anholt.net>
Acked-by: Scott Branden <sbranden@broadcom.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>