drm/radeon/r600_cs: Fix possible int overflows in r600_cs_check_reg()

While improbable, there may be a chance of hitting integer
overflow when the result of radeon_get_ib_value() gets shifted
left.

Avoid it by casting one of the operands to larger data type (u64).

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: 1729dd3 ("drm/radeon/kms: r600 CS parser fixes")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/r600_cs.c

@@ -1275,7 +1275,7 @@ static int r600_cs_check_reg(struct radeon_cs_parser *p, u32 reg, u32 idx)
 			return -EINVAL;
 		}
 		tmp = (reg - CB_COLOR0_BASE) / 4;
-		track->cb_color_bo_offset[tmp] = radeon_get_ib_value(p, idx) << 8;
+		track->cb_color_bo_offset[tmp] = (u64)radeon_get_ib_value(p, idx) << 8;
 		ib[idx] += (u32)((reloc->gpu_offset >> 8) & 0xffffffff);
 		track->cb_color_base_last[tmp] = ib[idx];
 		track->cb_color_bo[tmp] = reloc->robj;
@@ -1302,7 +1302,7 @@ static int r600_cs_check_reg(struct radeon_cs_parser *p, u32 reg, u32 idx)
 					"0x%04X\n", reg);
 			return -EINVAL;
 		}
-		track->htile_offset = radeon_get_ib_value(p, idx) << 8;
+		track->htile_offset = (u64)radeon_get_ib_value(p, idx) << 8;
 		ib[idx] += (u32)((reloc->gpu_offset >> 8) & 0xffffffff);
 		track->htile_bo = reloc->robj;
 		track->db_dirty = true;