Revert "coredump: Snapshot the vmas in do_coredump"

This reverts commit 936c8be4.

It breaks the abi and is not needed for Android devices so it can be
dropped.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I2af6e8472f55475bbb841e04ad18a84fdd2d9379