Add hclk entry for the atmel_lcdfb bus clock.

On at91sam9261, at91sam9g10 and at32ap the bus clock has to be enabled
as well as the peripheral clock. Add the appropriate lookup entries to
these SOCs and fake clocks to the SOCs that do not use it.

This allows us to get rid of the conditional enabling of the clocks in
the driver which relied on the cpu_is macros.

Tested on at91sam9263 and at91sam9g45, compile-tested for other
AT91-SOCs, and untested for AVR32.
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NNicolas Ferre <nicolas.ferre@atmel.com>