pipe-loader: fix off-by one error

pipe-loader: fix off-by one error

With earlier commit we've dropped the manual iteration over the fixed
size array and prepemtively set the variable storing the size, that is
to be returned. Yet we forgot to adjust the comparison, as before we
were comparing the index, now we're comparing the size.

Fixes: ff9cd8a67ca "pipe-loader: directly use
pipe_loader_sw_probe_null() at probe time"
Cc: mesa-stable@lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93091
Reported-by: Tom Stellard <thomas.stellard@amd.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Tested-by: Tom Stellard <thomas.stellard@amd.com>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>