ARM: at91: add Atmel ISI and ov2640 support on sam9m10g45 board

This patch adds:
- ov2640 sensor in at91sam9m10g45ek board
- support to use PCK as ISI_MCK. PCK's parent is managed at
  SoC level, e.g. at91sam9g45_devices.c

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Olof Johansson <olof@lixom.net>