uart: update the sysfs handler to use uart_get_info

The two patches needed are now in the tree. The first added the sysfs
interface and directly accesses the uartclk. The second provides a
proper interface for getting the values.

Wire them together.

This formes a basis for both get and set methods for any of the other uart
properties and we can now fill them out further.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>