video: host: vi: split out built-in code

video: host: vi: split out built-in code

VI driver could be a module. Those T124 sepcific functions are
used by other drivers, which make VI driver can't be built as a
module. So split them out to a separated file and always build
it into kernel, then the rest of vi.c driver can be a module.

Bug 1377330

Change-Id: I4a35ddd62f1c3caca09e596603f5f99b16159754
Signed-off-by: Bryan Wu <pengw@nvidia.com>
Reviewed-on: http://git-master/r/289327
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>