kernel: use V10 of mtd patchset adding support for "compatible" string

In the commit bde5e7a6 ("kernel: backport mtd implementation for
"compatible" in "partitions" subnode") patches that got accepted into
l2-mtd.git were backported to the kernels 4.9 and 4.14. Unfortunately
there was a regression report, patches were dropped and never reached
4.16.

This commit replaces these pseudo-backports with the latest version
that includes regression fix and futher changes that were requested.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>