[PATCH] qe: add function qe_clock_source

[Scott Wood]

Timur Tabi wrote:
> UART, for instance, can use a CLK signal, but I wrote the driver to only 
> support BRGs because there are plenty of them and it's a lot simpler.  But 
> someone, for instance, could wire up his board to want to use external clocks 
> for some UARTs, and so he'd need to modify the driver.

In the absence of a BRG, the driver should just not support changing the 
baud rate -- it shouldn't fail to function.

-Scott