drm/amd/amdgpu: fix comparison pointer to bool warning in gfx_v9_0.c

Fixes coccicheck warning:

drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:2805:5-11: WARNING: Comparison to bool
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c

@@ -2800,7 +2800,7 @@ static void pwr_10_0_gfxip_control_over_cgpg(struct amdgpu_device *adev,
 	uint32_t default_data = 0;
 
 	default_data = data = RREG32(SOC15_REG_OFFSET(PWR, 0, mmPWR_MISC_CNTL_STATUS));
-	if (enable == true) {
+	if (enable) {
 		/* enable GFXIP control over CGPG */
 		data |= PWR_MISC_CNTL_STATUS__PWR_GFX_RLC_CGPG_EN_MASK;
 		if(default_data != data)