dt-bindings: drop Sagar Kadam from SiFive binding maintainership

dt-bindings: drop Sagar Kadam from SiFive binding maintainership

Sagar's email listed in maintainers is bouncing as his division was sold
off by the company. I attempted to contact him some days ago on what the
bounce email told me was his new contact information, but am yet to
receive a response.

Paul and Palmer are listed on each of the bindings, both of whom were
alive & well as of Wednesday so the bindings remain maintained.

CC: Sagar Kadam <sagar.kadam@openfive.com>
CC: Sagar Kadam <sagar.kadam@sifive.com>
Link: https://lore.kernel.org/all/785425ca-4000-a7e4-16d6-4d68c91b158d@kernel.org/
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20230217180035.39658-1-conor@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>