r600/llvm: initialize radeon_llvm_binary

r600/llvm: initialize radeon_llvm_binary

use memset to initialize to 0's... otherwise code_size and config_size
could be uninitialized when read later in this method.

It's also hard to do NULL checks on uninitialized pointers.

Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
v2: Fix indentation

CC: "10.0" <mesa-stable@lists.freedesktop.org>