Install VINTF fragments over module

Previously VINTF fragments in keymint / wifi APEX was installed with
prebuilt_etc module. However, as vintf_fragment module is being used
within the APEX, this prebuilt_etc module is no longer required. This
change removes a prebuilt_etc module which installed VINTF fragments in
the keymint / wifi APEX.

Bug: 363105686
Test: AOSP CF x86_64 build succeeded
Change-Id: I76af1485ae0aa00b051eec16bfc1daf1c9b8a0ea
Merged-In: I76af1485ae0aa00b051eec16bfc1daf1c9b8a0ea