tegra2: Clean up board code a little

tegra2: Clean up board code a little

This removes clock_init() and pinmux_init() which are names better suited
to those respective modules. By moving board_init_f() to the bottom of the
file we can remove the need for so many functions in the board.h header file.

The only clock/pinmux/gpio init we need to do prior to relocation is
for the UART.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Tom Warren <twarren@nvidia.com>