i965/blorp: Turn blorp_surface_info into a C-style struct

i965/blorp: Turn blorp_surface_info into a C-style struct

This commit is mostly mechanical except that it changes where we set the
swizzle.  Previously, the blorp_surface_info constructor defaulted the
swizzle to SWIZZLE_XYZW.  Now, we memset to zero and fill out the swizzle
when we setup the rest of the struct.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>