Aligning phys_level0_sa by the compression block dimension prior to
mipmap layout causes the layout of compressed surfaces to differ from
the sampler's expectations in certain cases. The hardware docs agree:

From the BDW PRM, Vol. 5, Compressed Mipmap Layout,

   The compressed mipmaps are stored in a similar fashion to
   uncompressed mipmaps [...]

   The following exceptions apply to the layout of compressed (vs.
   uncompressed) mipmaps:
      * [...]
      * The dimensions of the mip maps are first determined by applying
	the sizing algorithm presented in Non-Power-of-Two Mipmaps
	above. Then, if necessary, they are padded out to compression
	block boundaries.

The last bullet indicates that alignment should not be done for
calculating a miplevel's dimensions, but rather for determining miplevel
placement/padding. Comply with this text by removing the extra
alignment.

Fixes some fbo-generatemipmap-formats piglit failures on all tested
platforms (SNB-KBL).

v2:
- Note fixed platforms.
- Update some consumers via a helper function.

Cc: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>