zink/ntv: Don't call free() on ralloc'd memory
Caught this with an LTO build:
[1465/1465] Linking target src/gallium/targets/dri/libgallium_dri.so
In function ‘spirv_shader_delete’,
inlined from ‘nir_to_spirv’ at ../src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c:3907:7:
../src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c:3916:4: warning: ‘free’ called on pointer ‘block_1394’ with nonzero offset 48 [-Wfree-nonheap-object]
3916 | FREE(s);
| ^
../src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c: In function ‘nir_to_spirv’:
../src/util/ralloc.c:133:18: note: returned from ‘malloc’
133 | void *block = malloc(align64(size + sizeof(ralloc_header),
| ^
Since s->words is allocated on the same ralloc context we can simplify further by freeing the context all at once.