cc3200: Move pinmux and UART initialization to PRE_KERNEL_1

Previously, cc3200_launchxl board was not able to show the
Zephyr Boot Banner, as that required early initialization
of the UART driver, which was done POST_KERNEL.

This patch moves the pinmux and UART driver initialization
to PRE_KERNEL_1, allowing early printk, and the Boot Banner
to show.

Change-Id: I84a7c20c1d5bdc3de150dc6bb0adebc9a2d9f5cb
Signed-off-by: Gil Pitney <gil.pitney@linaro.org>