drm/radeon: fix uninitialized size issue in radeon_vce_cs_parse()

On the off chance that command stream passed from userspace via
ioctl() call to radeon_vce_cs_parse() is weirdly crafted and
first command to execute is to encode (case 0x03000001), the function
in question will attempt to call radeon_vce_cs_reloc() with size
argument that has not been properly initialized. Specifically, 'size'
will point to 'tmp' variable before the latter had a chance to be
assigned any value.

Play it safe and init 'tmp' with 0, thus ensuring that
radeon_vce_cs_reloc() will catch an early error in cases like these.

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

Fixes: 2fc5703a ("drm/radeon: check VCE relocation buffer range v3")
Cc: stable@vger.kernel.org
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_vce.c

@@ -557,7 +557,7 @@ int radeon_vce_cs_parse(struct radeon_cs_parser *p)
 {
 	int session_idx = -1;
 	bool destroyed = false, created = false, allocated = false;
-	uint32_t tmp, handle = 0;
+	uint32_t tmp = 0, handle = 0;
 	uint32_t *size = &tmp;
 	int i, r = 0;