regulator: Update da9121 bindings

commit  e46f59488745f598156d480754e1476f8d9742e4 from
https://github.com/Xilinx/linux-xlnx.git xlnx_rebase_v5.10

Sync da9121 bindings with the mainline version. Delete the txt file
and add yaml.

Signed-off-by: Raviteja Narayanam <raviteja.narayanam@xilinx.com>
State: pending
Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>