xloader: Panda - refactor mux define into struct array

xloader: Panda - refactor mux define into struct array

There's a giant #define that is just unrolled code to
write a constant to a constant address.

This patch converts the address and data content to be
an array of structs, and changed the mux init code
to walk through the array doing the writes.

Signed-off-by: Andy Green <andy.green@linaro.org>
Signed-off-by: Anand Gadiyar <gadiyar@ti.com>