Revert "xfrm: add forgotten nla_policy for XFRMA_MTIMER_THRESH"

This reverts commit 61481169 which is
commit 5e242470 upstream.

It breaks the build, as the dependant patch, 4e484b3e ("xfrm: rate
limit SA mapping change message to user space"), was reverted from the
Android kernel tree when it was merged from the LTS release it was
contained in (5.10.94).  So there is nothing to "fix" here in this tree,
and it breaks the build with it present.

Fixes: 61481169 ("xfrm: add forgotten nla_policy for XFRMA_MTIMER_THRESH")
Change-Id: I30783bfd7e4b827028cbc27bdc756d8c6e8fb6d5
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>