mmc: sdhci-of-at91: use SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST quirk

The Atmel sdhci device needs the
SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST quirk. Without it, the
internal clock could never stabilised when changing the sd clock
frequency.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>