nimble/host: Restore key size for LTK
nimble/host: Restore key size for LTK

When LTK is restored successfully we also need to update key size for
proc with proper value as otherwise we default to 0 which means that
e.g. any characteristic which requires proper key size for read/write
cannot be accessed.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble