kmodloader: Increase path array size to make it always fit

kmodloader: Increase path array size to make it always fit

When DEF_MOD_PATH (10 bytes), s (max 255 bytes) and ver.release (max 64
bytes) are all written into path, 256 bytes will not fit, increase the
available size. All given sizes are given without terminating NULL byte
and we add one byte to store the NULL byte.

GCC 9.1 warns about this condition and we treat warnings as errors in
ubox.

Reported-by: Joseph Benden <joe@benden.us>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>