radv/video: Match function definitions to declarations

radv/video: Match function definitions to declarations

This adds the same function attributes from definitions to declarations
and fixes the following compiler errors for 32 bit Windows OS.

../src/amd/vulkan/radv_video.c:270:1: error: conflicting types for 'radv_CreateVideoSessionKHR'
src/amd/vulkan/radv_entrypoints.h:3963:34: note: previous declaration of 'radv_CreateVideoSessionKHR'
../src/amd/vulkan/radv_video.c:319:1: error: conflicting types for 'radv_DestroyVideoSessionKHR'
src/amd/vulkan/radv_entrypoints.h:3971:30: note: previous declaration of 'radv_DestroyVideoSessionKHR'

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24460>