Revert "mtd: fix 'part' field data corruption in mtd_info"

This reverts commit 6f2bf9c5 which is
commit 37c5f9e8 upstream.

It breaks the ABI and will be brought back later in an ABI-safe way.

Bug: 161946584
Change-Id: Ia8f3f31c12c00cf304855fc77e033e7fd3b00498
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>