pinmux: Rename frdm_k64f pinmux driver to k64

The k64 pinmux driver can be used for any k64 board, not just frdm_k64f,
therefore renaming the driver accordingly.

Change-Id: I45e96d4a5ff6aa859d0f57fe098e44a8ae5283d1
Signed-off-by: Maureen Helm <maureen.helm@nxp.com>
9 files changed