Update the check_block_eraser function to use probe_opcode to see if the
given block_eraser is supported by the spi master. This will help to get
a real count of usable block_erasers.
Change-Id: I6591a84ae1fe5bc1648051cc30b9393450033852
Signed-off-by: Aarya Chaumal <aarya.chaumal@gmail.com>