ata: sata_mv: Fix incorrect string length computation in mv_dump_mem()

ata: sata_mv: Fix incorrect string length computation in mv_dump_mem()

snprintf() returns the "number of characters which *would* be generated for
the given input", not the size *really* generated.

In order to avoid too large values for 'o' (and potential negative values
for "sizeof(linebuf) o") use scnprintf() instead of snprintf().

Note that given the "w < 4" in the for loop, the buffer can NOT
overflow, but using the *right* function is always better.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>