erofs-utils: lib: suppress a false-positive warning in kite-deflate

erofs-utils: lib: suppress a false-positive warning in kite-deflate

`gcc (Debian 13.2.0-2) 13.2.0` gives the following report:

kite_deflate.c: In function 'kite_deflate_writeblock':
kite_deflate.c:428:57: warning: 'distLevels' may be used uninitialized
[-Wmaybe-uninitialized]
428 |                                   fixed ? 5 :
    distLevels[distSlot]);
|                                                         ^
kite_deflate.c:393:34: note: 'distLevels' was declared here
  393 |         const u8 *litLenLevels, *distLevels;

Actually, `distLevels` won't be used in the static-huffman mode.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230912032701.8288-1-hsiangkao@linux.alibaba.com