DT: bindings: remove bcm2835-sdhci

The sdhci-iproc also supports bcm2835. So this binding is obsolete.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>