drm: i915: Adapt to -Walloc-size

drm: i915: Adapt to -Walloc-size

GCC 14 introduces a new -Walloc-size included in -Wextra which errors out
like:
```
drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c: In function ‘eb_copy_relocations’:
drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:1681:24: error: allocation of insufficient size ‘1’ for type ‘struct drm_i915_gem_relocation_entry’ with size ‘32’ [-Werror=alloc-size]
 1681 |                 relocs = kvmalloc_array(size, 1, GFP_KERNEL);
      |                        ^

```

So, just swap the number of members and size arguments to match the prototype, as
we're initialising 1 element of size `size`. GCC then sees we're not
doing anything wrong.

Signed-off-by: Sam James <sam@gentoo.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231107215538.1891359-1-sam@gentoo.org