radeon/llvm: Allocate space for kernel metadata operands

radeon/llvm: Allocate space for kernel metadata operands

Previously, we were assuming that kernel metadata nodes only had 1 operand.

Kernels which have attributes can have more than 1, e.g.:
!0 = metadata !{void (i32 addrspace(1)*)* @testKernel, metadata !1}
!1 = metadata !{metadata !"work_group_size_hint", i32 4, i32 1, i32 1}

Attempting to get the kernel without the correct number of attributes led
to memory corruption and luxrays crashing out.

Fixes the cl/program/execute/attributes.cl piglit test.

Signed-off-by: Aaron Watry <awatry@gmail.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76223
CC: "10.2" <mesa-stable@lists.freedesktop.org>