sepolicy: Add policy to allow access to rmnet_mhi0 RPS entry

This is needed to set the receive packet steering entry.
Fixes the following denial -

avc: denied { read write } for comm="netmgrd" name="rps_cpus"
dev="sysfs" ino=79460 scontext=u:r:netmgrd:s0
tcontext=u:object_r:sysfs:s0 tclass=file permissive=0

CRs-fixed: 2425568
Change-Id: Idc94fbef7ed922a6d2376fd82bdb6cb45ff0d536