[Patch] ringqueue.cpp: fix gcc6 build

[mt]

In compute_order(), gcc6 warns '-Werror=misleading-indentation', but I think if() at line 40 is not in for() block. So I separate for() and if().

C++ /home/haiku/haiku/haiku/generated-gcc6/objects/haiku/x86/release/add-ons/accelerants/radeon_hd/ringqueue.o 
/home/haiku/haiku/haiku/src/add-ons/accelerants/radeon_hd/ringqueue.cpp: In function 'int compute_order(long unsigned int)':
/home/haiku/haiku/haiku/src/add-ons/accelerants/radeon_hd/ringqueue.cpp:39:2: error: this 'for' clause does not guard... [-Werror=misleading-indentation]
  for (order = 0, tmp = size; tmp >>= 1; ++order);
  ^~~
/home/haiku/haiku/haiku/src/add-ons/accelerants/radeon_hd/ringqueue.cpp:40:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   if (size & ~(1 << order))
   ^~
cc1plus: all warnings being treated as errors

[korli]

+1

[kallisti5]

Pushed in hrev50301 Thanks for the patch!