ARM: 6406/1: at91sam9g45: fix i2c bus speed

Use a correct udelay value to get bus speed around 100KHz. The udelay
value was most likely copied from the older devices, but the 9g45
is signicantly faster (400MHz, DDR, ..), so a udelay of 2 gives a
bus speed of around 190KHz, which is too fast for some devices.
A udelay value of 5 gives a bus speed of around 90KHz here.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>