doc/nvme-write: fix short hand argument for --block-size

The short-hand for the --block-size is -b not -c.

Signed-off-by: Daniel Wagner <[email protected]>

Author: igaw

Documentation/nvme-write.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 [verse]
 'nvme-write' <device> [--start-block=<slba> | -s <slba>]
 			[--block-count=<nlb> | -c <nlb>]
-			[--block-size=<size> | -c <size>]
+			[--block-size=<size> | -b <size>]
 			[--data-size=<size> | -z <size>]
 			[--metadata-size=<size> | -y <size>]
 			[--ref-tag=<reftag> | -r <reftag>]