dm: am335x: Remove serial options from CONFIG_SYS_EXTRA_OPTIONS

dm: am335x: Remove serial options from CONFIG_SYS_EXTRA_OPTIONS

With these options in place it is not possible to change the serial port
using 'make menuconfig' or similar. It seems to result in duplicate
defines.

For example:

In file included from include/linux/kconfig.h:4:0,
                 from <command-line>:0:
include/generated/autoconf.h:20:0: note: this is the location of the previous definition
 #define CONFIG_CONS_INDEX 2
 ^

The default option seems to be 1 anyway, in board/ti/am335x/Kconfig.

Remove the options so that we can adjust the serial port if required.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Tom Rini <trini@ti.com>