This patch replaces the pinmux APIs that require users to look up an arbitrary
function number for the desired function of each pin. The replacement API
functions have intuitive names and permit users to pass board-level IO port
numbers. The API functions internally convert those to CPU-level port numbers
when necessary. Furthermore, when configuring a pin to be a digital input or
output, those API functions also perform the corresponding configuration
operation on the CPU-level GPIO port. The revised APIs halt when users attempt
to configure a currently-unsupported GPIO, specifically those in the GPIO_SUS
port range and those implemented on the expander chip EXP2. This also means
that such ports are left unconfigured during initialization, whereas the
pinmuxing for them was setup by the old implementation.