nvme/029: fix local variable declarations

nvme/029: fix local variable declarations

The syntax for local variables declarations uses whitespace as separator
and not commas:

tests/nvme/029: line 24: local: `bs,': not a valid identifier
tests/nvme/029: line 24: local: `size,': not a valid identifier
tests/nvme/029: line 24: local: `img,': not a valid identifier

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>