meta: Fix blitting a framebuffer with renderbuffer attachment

meta: Fix blitting a framebuffer with renderbuffer attachment

This patch fixes a case of framebuffer blitting with renderbuffer
as color attachment and GL_LINEAR filter. Meta implementation of
glBlitFrambuffer() converts source color buffer to a texture and
uses it to do the scaled blitting in to destination buffer. Using
the exact source rectangle to create the texture does incorrect
linear filtering along the edges. This patch makes the changes to
extend the texture edges by one pixel in x, y directions. This
ensures correct linear filtering.
It fixes failing piglit fbo-attachments-blit-scaled-linear test.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
CC: "9.2" <mesa-stable@lists.freedesktop.org>
CC: "9.1" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Paul Berry <stereotype441@gmail.com>