MAINTAINERS: Update the entry for MHI bus

Since Hemant is not carrying out any maintainership duties let's make
him as a dedicated reviewer. Also add the new mailing lists dedicated
for MHI in subspace mailing list server.
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20211019133901.173966-1-manivannan.sadhasivam@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -12214,7 +12214,8 @@ F:	arch/arm64/boot/dts/marvell/armada-3720-uDPU.dts
 
 MHI BUS
 M:	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
-M:	Hemant Kumar <hemantk@codeaurora.org>
+R:	Hemant Kumar <hemantk@codeaurora.org>
+L:	mhi@lists.linux.dev
 L:	linux-arm-msm@vger.kernel.org
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mani/mhi.git