This function is more complicated than necessary.

If we change from scnprintf() to snprintf() that lets us remove the if
bytes_wrote < sizeof(protocol) checks.  Also, we can use bytes_wrote ? ","
: "" to print the comma and remove the separate if statement and the
"is_string_nonempty" variable.

[mkp: a few formatting cleanups and s/wrote/written/]

Link: https://lore.kernel.org/r/20210916132605.GF25094@kiliSigned-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>