ARM: davinci: serial: get rid of davinci_uart_config

"struct davinci_uart_config" was introduced to specify
UART ports brought out or enabled on the board. But
none of the boards use it for that purpose and we are
not going to add anymore board files, so remove the
structure.

Signed-off-by: Manjunathappa, Prakash <prakash.pm@ti.com>
Suggested-by: Sekhar Nori <nsekhar@ti.com>
[nsekhar@ti.com: split patch to remove davinci_serial_setup_clk()
		 changes.]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>