i965: extend fast texture upload

i965: extend fast texture upload

Extend the fast texture upload from BGRA X-tiled to include RGBA,
Alpha/Luminance, and Y-tiled.  Speed improvements, measured with
mesa demos teximage program, on 256 x 256 texture, in MB/s, on a
Sandy Bridge (Ivy is comparable):

              before  after   increase
BGRA/X-tiled   3266    4524    1.39x
BGRA/Y-tiled   1739    3971    2.28x
RGBA/X-tiled    474    4694    9.90x
RGBA/Y-tiled    477    3368    7.06x
   L/X-tiled   1268    1516    1.20x
   L/Y-tiled   1439    1581    1.10x

v2: Cosmetic changes only: reformat and reword comments, make doxygen-friendly,
    rename variables, use existing macros, add an assert.

Signed-off-by: Frank Henigman <fjhenigman@google.com>
Reviewed-and-tested-by: Chad Versace <chad.versace@linux.intel.com>