r600g/compute: Tidy a bit compute_memory_finalize_pending

Explanation of the changes, as requested by Tom Stellard:

Let's take need after is calculated as
item->size_in_dw+2048 - (pool->size_in_dw - allocated)

BEFORE:
If need is positive or 0:
    we calculate need += 1024 - (need % 1024), which is like
        cealing to the nearest multiple of 1024, for example
        0 goes to 1024, 512 goes to 1024 as well, 1025 goes
        to 2048 and so on. So now need is always possitive,
        we do compute_memory_grow_pool, check its output
        and continue.

If need is negative:
    we calculate need += 1024 - (need % 1024), in this case
        we will have negative numbers, and if need is
        [-1024:-1] 0, so now we take the else, recalculate
        need as need = pool->size_in_dw / 10 and
        need += 1024 - (need % 1024), we do
        compute_memory_grow_pool, check its output and continue.

AFTER:
If need is positive or 0:
    we jump the if, calculate need += 1024 - (need % 1024)
        compute_memory_grow_pool, check its output and continue.

If need is negative:
    we enter the if, and need is now pool->size_in_dw / 10.
        Now we calculate need += 1024 - (need % 1024)
        compute_memory_grow_pool, check its output and continue.

Reviewed-by: Tom Stellard <thomas.stellard@amd.com>

src/gallium/drivers/r600/compute_memory_pool.c

@@ -319,20 +319,15 @@ int compute_memory_finalize_pending(struct compute_memory_pool* pool,
 			int64_t need = item->size_in_dw+2048 -
 						(pool->size_in_dw - allocated);
 
+			if (need < 0) {
+				need = pool->size_in_dw / 10;
+			}
+
 			need += 1024 - (need % 1024);
 
-			if (need > 0) {
-				err = compute_memory_grow_pool(pool,
-						pipe,
-						pool->size_in_dw + need);
-			}
-			else {
-				need = pool->size_in_dw / 10;
-				need += 1024 - (need % 1024);
-				err = compute_memory_grow_pool(pool,
-						pipe,
-						pool->size_in_dw + need);
-			}
+			err = compute_memory_grow_pool(pool,
+					pipe,
+					pool->size_in_dw + need);
 
 			if (err == -1)
 				return -1;