svga: force direct map for transfering multiple slices

svga: force direct map for transfering multiple slices

With commit fb9fe35, we start using transfer_inline_write
for memcpy of TexSubImage. But SurfaceDMA command does not work
well with texture array. This patch forces direct map when
transfering multiple slices of a texture array.

Fixes piglit regression "texelFetch fs sampler1DArray"

Tested with MTT piglit, glretrace, conform.

Reviewed-by: Sinclair Yeh <syeh@vmware.com>