UPSTREAM: selinux: make "selinux_policycap_names[]" const char *

Those strings aren't written.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

(cherry picked from commit 89f5bebcf0401dac470756869587a50dd72ff7b5)
Change-Id: I968b2f6197b2d749b3786089b942655d1880258a
Bug: 140252993
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>