MAINTAINERS: phy: Move Kishon Vijay Abraham I to credits

MAINTAINERS: phy: Move Kishon Vijay Abraham I to credits

There wasn't much of reviewing activity from Kishon of PHY subsystem
during last few years [1] and last maintainer commit is from 2020, so
move Kishon to Credits to indicate that PHY subsystem has only one
active maintainer.  Thank you Kishon for working on the PHY subsystem
and for all the maintenance effort.

Link: https://lore.kernel.org/all/?q=f%3A%22Kishon+Vijay+Abraham+I%22
Cc: Kishon Vijay Abraham I <kishon@kernel.org>
Cc: Kishon Vijay Abraham I <kvijayab@amd.com>
Cc: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://patch.msgid.link/20251120175537.171340-2-krzk@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>