libmtd: compile fix for linux header changes.

libmtd: compile fix for linux header changes.

In the Linux kernel source, mtd/mtd-user.h had a change
'mtd: mtd-user: remove stdint.h include'
(137d36af4a53858b8db7ca83c8480247118b8bdf)

This causes the uint8_t/uint64_t types to be undefined in libmtd.h
now, as they were implicitly coming from it before.

Import stdint.h explicitly into libmtd.h to resolve this.

X-URL: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=137d36af4a53858b8db7ca83c8480247118b8bdf
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>