drm/i915/selftests: Let igt_vma_partial et al breathe

Give the scheduler a chance to breathe by calling cond_resched() as some
of the loops may take some time on slower machines, and so catch the
attention of the watchdogs.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111196
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190723095800.2820-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/selftests/i915_vma.c

@@ -193,6 +193,8 @@ static int igt_vma_create(void *arg)
 			list_del_init(&ctx->link);
 			mock_context_close(ctx);
 		}
+
+		cond_resched();
 	}
 
 end:
@@ -341,6 +343,8 @@ static int igt_vma_pin1(void *arg)
 				goto out;
 			}
 		}
+
+		cond_resched();
 	}
 
 	err = 0;
@@ -597,6 +601,8 @@ static int igt_vma_rotate_remap(void *arg)
 					}
 
 					i915_vma_unpin(vma);
+
+					cond_resched();
 				}
 			}
 		}
@@ -752,6 +758,8 @@ static int igt_vma_partial(void *arg)
 
 				i915_vma_unpin(vma);
 				nvma++;
+
+				cond_resched();
 			}
 		}
 
@@ -961,6 +969,8 @@ static int igt_vma_remapped_gtt(void *arg)
 				}
 			}
 			i915_vma_unpin_iomap(vma);
+
+			cond_resched();
 		}
 	}