All identifiers, regardless of use, that start with two underscores are
reserved. This means they can't be used in header guards.

The style that this project is now to use the full name of the file in
capital letters followed by 'H'. For example, for a file called
"uart_example.h", the header guard is UART_EXAMPLE_H.

The exceptions are files that are imported from other projects:

- CryptoCell driver
- dt-bindings folders
- zlib headers

Change-Id: I50561bf6c88b491ec440d0c8385c74650f3c106e
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This patch defines:

- The full range of IO-mux register offsets relative to the base address of
  the IO-mux block base address.

- The bits for muxing the UART1 TX/RX lines.

- The bits for muxing the UART6 TX/RX lines.

- The pad control pad bits for the UART

Two functions are provided to configure pad muxes:

- void io_muxc_set_pad_alt_function(pad_mux_offset, alt_function)
  Takes a pad_mux_offset and sets the alt_function bit-mask supplied.
  This will have the effect of switching the pad into one of its defined
  peripheral functions. These peripheral function modes are defined in the
  NXP documentation and need to be referred to in order to correctly
  configure a new alternative-function.

- void io_muxc_set_pad_features(pad_feature_offset, pad_features)
  Takes a pad_feature_offset and applies a pad_features bit-mask to the
  indicated pad.
  This function allows the setting of PAD drive-strength, pull-up values,
  hysteresis glitch filters and slew-rate settings.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>