boards: arm: Update frdm_k64f and mimxrt10{60,64}_evk board docs

Updates board documentation for several NXP boards to reflect currently
supported features, NXP documentation links, clarifications on debug
probes, additional troubleshooting tips, and some minor editorial
changes.

Signed-off-by: Derek Snell <derek.snell@nxp.com>
Signed-off-by: Maureen Helm <maureen.helm@nxp.com>