Revert "tracing/hist: Support POLLPRI event for poll on histogram"

This reverts commit d24e5e63 which is
commit 66fc6f52 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I2678f5c279e4b990895db6dae3b83af23dbded00
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>