Device permissions is S_IALLUGO, with many unnecessary bits. Remove them
and also remove read and write permissions from group and others.

Before the change:
crwsrwsrwt    1 0        0          10, 125 Nov 25 13:59 /dev/virtual_nci

After the change:
crw-------    1 0        0          10, 125 Nov 25 14:05 /dev/virtual_nci
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Reviewed-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: NBongsu Jeon <bongsu.jeon@samsung.com>
Link: https://lore.kernel.org/r/20211125141457.716921-1-cascardo@canonical.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>