UPSTREAM: random: ignore GRND_RANDOM in getentropy(2)

The separate blocking pool is going away.  Start by ignoring
GRND_RANDOM in getentropy(2).

This should not materially break any API.  Any code that worked
without this change should work at least as well with this change.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/705c5a091b63cc5da70c99304bb97e0109be0a26.1577088521.git.luto@kernel.org


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
(cherry picked from commit 48446f198f9adcb499b30332488dfd5bc3f176f6)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 148665638
Change-Id: I2f99c4cdb5815951b0d42171c8fe4a4a671a2210