Now that we have a more generic ksdk pinmux driver that can be used
across multiple Kinetis SoCs, deprecate the specific k64 pinmux driver.
Jira: ZEP-1393
Change-Id: I11cfe9a53746a6e85eced2a7cecf0396d42a7a19
Signed-off-by: Maureen Helm <maureen.helm@nxp.com>