svga: fix texture array update regression

svga: fix texture array update regression

With commit fb9fe35, we start using transfer_inline_write
for memcpy TexSubImage path, but that triggers a regression with
texture array in the svga driver.

With this patch, the direct map code will update the texture array
correctly.

Fixes VMware bug 1679293.

Tested with MTT piglit, glretrace, conform.

Reviewed-by: Brian Paul <brianp@vmware.com>