proxy: fix indentation warning

proxy: fix indentation warning

Fixes the following warning caused by a bad indentation:

src/proxy.c: In function ‘proxy_set’:
src/proxy.c:161:17: warning: this ‘for’ clause does not guard... [-Wmisleading-indentation]
  161 |                 for (i = 0; i < downlinks_cnt && downlinks[i] == iface->iface->ifindex; ++i);
      |                 ^~~
src/proxy.c:162:25: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘for’
  162 |                         if (i == downlinks_cnt)
      |                         ^~

Signed-off-by: Vladimír Chlup <[email protected]>
Link: https://github.com/openwrt/omcproxy/pull/13
Signed-off-by: Álvaro Fernández Rojas <[email protected]>