Revert "fs: check FMODE_LSEEK to control internal pipe splicing"

This reverts commit ab37175d which is
commit 97ef77c5 upstream.

It causes VTS failures for some reason and needs to be reverted for now
until the root cause is tracked down.

Bug: 247779313
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I19341cd7c5cf90780804e77dbbf2e32ecc2644fc