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

In the Linux kernel, the following vulnerability has been resolved: 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. (cherry picked from commit 2d52de55f9ee7aaee0e09ac443f77855989c6b68)