The TI_K3_M4_REMOTEPROC Kconfig entry selects OMAP2PLUS_MBOX, but that
driver in turn depends on other things, which the k4-m4 driver didn't.

This causes a Kconfig time warning:

  WARNING: unmet direct dependencies detected for OMAP2PLUS_MBOX
    Depends on [n]: MAILBOX [=y] && (ARCH_OMAP2PLUS || ARCH_K3)
    Selected by [m]:
    - TI_K3_M4_REMOTEPROC [=m] && REMOTEPROC [=y] && (ARCH_K3 || COMPILE_TEST [=y])

because you can't select something that is unavailable.

Make the dependencies for TI_K3_M4_REMOTEPROC match those of the
OMAP2PLUS_MBOX driver that it needs.

Fixes: ebcf9008 ("remoteproc: k3-m4: Add a remoteproc driver for M4F subsystem")
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Martyn Welch <martyn.welch@collabora.com>
Cc: Hari Nagalla <hnagalla@ti.com>
Cc: Andrew Davis <afd@ti.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>