media: em28xx: fix two smatch warnings

Use sizeof instead of ARRAY_SIZE to fix this smatch warning:

drivers/media/usb/em28xx/em28xx-i2c.c:952 em28xx_do_i2c_scan() warn: calling memset(x, y, ARRAY_SIZE());

Do the same for the em28xx_hash_mem() call in the same function.
smatch didn't pick that up, but there too it should use sizeof instead
of ARRAY_SIZE.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>