staging: rtl8192u: Replaces symbolic permissions with octal permissions

Solves following checkpatch.pl issue:
WARNING: Symbolic permissions 'S_IRUGO' are not preferred. Consider
using octal permissions '0444'.

Signed-off-by: Camylla Goncalves Cantanheide <c.cantanheide@gmail.com>
Link: https://lore.kernel.org/r/20200317071959.556-1-c.cantanheide@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>