drm/vmwgfx: Fix frame-size warning in vmw_mksstat_add_ioctl

Function vmw_mksstat_add_ioctl allocates three big arrays on stack.
That triggers frame-size [-Wframe-larger-than=] warning. Refactor
that function to use kmalloc_array instead.

v2: Initialize page to null to avoid possible uninitialized use of it,
    spotted by the kernel test robot <lkp@intel.com>

Signed-off-by: Martin Krastev <krastevm@vmware.com>
Reviewed-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Maaz Mombasawala <mombasawalam@vmware.com>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221022040236.616490-3-zack@kde.org