remoteproc: mediatek: Change the snprintf() checking

remoteproc: mediatek: Change the snprintf() checking

The snprintf() calls here work but they have several minor style issues:

1) It uses ARRAY_SIZE() which is the number of elements in an array.
   Since were talking about char that works, but it's more common to
   use sizeof() which is the number of bytes.
2) The printf format is "%1d".  The "1" ensures we always print at
   least 1 character but since numbers all have at least 1 digit this
   can be removed.
3) The kernel implementation of snprintf() cannot return negative error
   codes.  Also these particular calls to snprintf() can't return zero
   and the code to handle that zero return is sort of questionable.
4) In the current kernel the only "core_id" we print is "0" but if it
   was more than 9 then the output would be truncated so GCC complains.
   Add an "a >= sizeof(scp_fw_file)" check for output which is too long.

Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/aP8agyKj73bLZrTQ@stanley.mountain
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>