galileo: Remove pinmux kconfigs for the board and reuse existing

Do not redefine the the pinmux configuration for the board, just use
the data directly. No other board will be using those, just the galileo.

Change-Id: If774bc5c4335021ae58a682224f092db23bc9f1b
Signed-off-by: Anas Nashif <anas.nashif@intel.com>