isl: Don't align phys_level0_sa by block dimension

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>
10 jobs for !937 with sent/fix/compressed-mipmaps in 10 minutes and 47 seconds (queued for 2 seconds)
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passed meson-clang #386188

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passed meson-clover #386192

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passed meson-main #386191

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passed meson-swr-glvnd #386187

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passed scons-win64 #386190

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