sepolicy_version: change current version to NN.m format

The sepolicy version takes SDK_INT.<minor> format. Make sure our
'current' policy version reflects the format and make it '100000.0'.
This ensures any vendor.img compiled with this will never work with
a production framework image either.

Make version_policy replace the '.' in version by '_' so secilc is
happy too.

This unblocks libvintf from giving out a runtme API to check vendor's
sepolicy version. The PLAT_PUBLIC_SEPOLICY_CURRENT_VERSION will
eventually be picked up from the build system.

(cherry-pick of commit 42f95984)

Bug: 35217573
Test: Build and boot sailfish.
      Boot sailfish with sepolicy compilation on device.
Signed-off-by: Sandeep Patil <sspatil@google.com>

Change-Id: Ic8b6687c4e71227bf9090018999149cd9e11d63b