md: avoid array overflow with bad v1.x metadata
md: avoid array overflow with bad v1.x metadata

We trust the 'desc_nr' field in v1.x metadata enough to use it
as an index in an array.  This isn't really safe.
So range-check the value first.

Signed-off-by: NeilBrown <1c00aa603bb92d594c03cff60ecf8e63b2a5bcb1@suse.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas