[PATCH] drm: powerplay: use div64_s64 instead of do_div

[Arnd Bergmann <arnd@arndb.de>]

The newly added code for Fiji creates a correct compiler warning
about invalid use of the do_div macro:

In file included from powerplay/hwmgr/ppatomctrl.c:31:0:
drivers/gpu/drm/amd/amdgpu/../powerplay/hwmgr/ppevvmath.h: In function 'fDivide':
drivers/gpu/drm/amd/amdgpu/../powerplay/hwmgr/ppevvmath.h:382:89: warning: comparison of distinct pointer types lacks a cast
     do_div(longlongX, longlongY); /*Q(32,32) divided by Q(16,16) = Q(16,16) Back to original format */

do_div() divides an unsigned 64-bit number by an unsigned 32-bit number.
The code instead wants to divide two signed 64-bit numbers, which is done
using the div64_s64 function.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 770911a3cfbb ("drm/amd/powerplay: add/update headers for Fiji SMU and DPM")
---
Found on ARM allmodconfig on yesterday's linux-next 

diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/ppevvmath.h b/drivers/gpu/drm/amd/powerplay/hwmgr/ppevvmath.h
index 42f2423cddea..411cb0fcdf98 100644
--- a/drivers/gpu/drm/amd/powerplay/hwmgr/ppevvmath.h
+++ b/drivers/gpu/drm/amd/powerplay/hwmgr/ppevvmath.h
@@ -379,7 +379,7 @@ fInt fDivide (fInt X, fInt Y)
 
     longlongX = longlongX << 16; /*Q(16,16) -> Q(32,32) */
 
-    do_div(longlongX, longlongY); /*Q(32,32) divided by Q(16,16) = Q(16,16) Back to original format */
+    div64_s64(longlongX, longlongY); /*Q(32,32) divided by Q(16,16) = Q(16,16) Back to original format */
 
     fQuotient.full = (int)longlongX;
     return fQuotient;