lib:crypto: Fix Coverity build

lib:crypto: Fix Coverity build

The Coverity build is failing with the following errors:

[1936/5164] Compiling lib/crypto/gkdi.c
In file included from /usr/lib64/gcc/x86_64-suse-linux/7/include/stdint.h:9:0,
                 from /usr/include/inttypes.h:27,
                 from ../../lib/crypto/../replace/replace.h:64,
                 from ../../source4/include/includes.h:23,
                 from ../../lib/crypto/gkdi.c:21:
../../lib/crypto/gkdi.c: In function ‘gkdi_get_key_start_time’:
../../lib/crypto/gkdi.c:197:4: error: initializer element is not constant
    UINT64_MAX /
    ^
../../lib/crypto/gkdi.c:197:4: note: (near initialization for ‘max_gkid.l0_idx’)
../../lib/crypto/gkdi.c:200:4: error: initializer element is not constant
    UINT64_MAX /
    ^
../../lib/crypto/gkdi.c:200:4: note: (near initialization for ‘max_gkid.l1_idx’)
../../lib/crypto/gkdi.c:204:4: error: initializer element is not constant
    UINT64_MAX / gkdi_key_cycle_duration %
    ^
../../lib/crypto/gkdi.c:204:4: note: (near initialization for ‘max_gkid.l2_idx’)

Fix the build by removing the ‘static’ specifier on this constant.

Signed-off-by: Jo Sutton <josutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>