msmnile: Add spmi and i2c-pmic devices to genfs_contexts

Define selinux context label for FG spmi device. While at it, add
the selinux context definition for smb1390 device also along with
SMB1355 alternate i2c address context definition.

Change-Id: I9d7c89a6fbbb2648d9c5a3e522b32c5e675c6534