scsi: ufs: Split the drivers/scsi/ufs directory

Split the drivers/scsi/ufs directory into 'core' and 'host' directories
under the drivers/ufs/ directory. Move shared header files into the
include/ufs/ directory. This separation makes it clear which header files
UFS drivers are allowed to include (include/ufs/*.h) and which header files
UFS drivers are not allowed to include (drivers/ufs/core/*.h).

Update the MAINTAINERS file. Add myself as a UFS reviewer.

Link: https://lore.kernel.org/r/20220511212552.655341-1-bvanassche@acm.org
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Avri Altman <avri.altman@wdc.com>
Cc: Bean Huo <beanhuo@micron.com>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Keoseong Park <keosung.park@samsung.com>
Tested-by: Bean Huo <beanhuo@micron.com>
Tested-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Acked-by: Avri Altman <avri.altman@wdc.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>