MAINTAINERS: Update my email address and maintainer level status

My employment with TI is ending tomorrow, so update the email address
entry in the maintainers file. Also, I don't expect to spend that much
time with maintaining TI code anymore, so downgrade the status level to
odd fixes only on areas where I remain as the main contact point for
now, and move myself as secondary contact point where someone else has
taken over the maintainership.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tero Kristo <kristo@kernel.org>
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Santosh Shilimkar <ssantosh@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20201217130721.23555-1-t-kristo@ti.com