hexiwear_k64: Update doc with new sensors and pinmuxing

Adds fxas21002 and max30101 sensors to the list of supported features in
the hexiwear_k64 board document. Updates the pinmux table with the
sensor pins and sorts it by port name, then pin number.

Change-Id: I7d4c2c3b7b0e6e52b34e5675ce957c3bc5d18d46
Signed-off-by: Maureen Helm <maureen.helm@nxp.com>