mtd: Introduce mtd_block_isreserved()

mtd: Introduce mtd_block_isreserved()

In addition to mtd_block_isbad(), which checks if a block is bad or
reserved, it's needed to check if a block is reserved only (but not
bad). This commit adds an MTD interface for it, in a similar fashion to
mtd_block_isbad().

While here, fix mtd_block_isbad() so the out-of-bounds checking is done
before the callback check.

Signed-off-by: Ezequiel Garcia <[email protected]>
Tested-by: Pekon Gupta <[email protected]>
Signed-off-by: Brian Norris <[email protected]>
[scottwood: Cherry-picked from Linux 8471bb73ba10ed67]
Signed-off-by: Scott Wood <[email protected]>