gf_w64.c: fix integer overflow
gf_w64.c: fix integer overflow

Fix for Coverity issue (from Ceph):

CID 1193089 (#1 of 1): Unintentional integer overflow (OVERFLOW_BEFORE_WIDEN)
 overflow_before_widen: Potentially overflowing expression 1 << g_r with type
 int (32 bits, signed) is evaluated using 32-bit arithmetic, and then used in
 a context that expects an expression of type uint64_t (64 bits, unsigned).

CID 1193090 (#1 of 1): Unintentional integer overflow (OVERFLOW_BEFORE_WIDEN)
 overflow_before_widen: Potentially overflowing expression 1 << g_s with type
 int (32 bits, signed) is evaluated using 32-bit arithmetic, and then used in
 a context that expects an expression of type uint64_t (64 bits, unsigned).

Signed-off-by: Danny Al-Gaaf <473e39ac77cf392f0dd9bacde8409de76c14d006@bisect.de>

ceph/gf-complete,ceph/gf-complete,ceph/gf-complete