BACKPORT: mips: vdso: Enable mips to use common headers

Enable mips to use only the common headers in the implementation of
the vDSO library.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul Burton <paulburton@kernel.org>
Link: https://lkml.kernel.org/r/20200320145351.32292-23-vincenzo.frascino@arm.com


(cherry picked from commit c135fc875ce363ff8405a8e64408bca0aa2a865b)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 154668398
Change-Id: I80936b5fbd4a2a7e0b7b2af29f4570129f02f678