drm/i915/i915_reg.h: fix the checkpatch SPACING issues

Because OCD.

Now seriously, commit 1aa920ea ("drm/i915: add register macro
definition style guide") has finally established a coding standard to
be followed by the rest of the file, and I've been trying to request
everybody to adhere to that since then. The problem is that when
someone adds a new line to a register that has the wrong style, these
people generally propagate the wrong style and I have to keep asking
them to drive-by fix the whole register, which is not something I like
to do and also creates extra work for them. Or I can ignore the
propagation of the wrong coding style and feel anxious about it. On
top of that, we now have our CI happily reminding us about these
problems, which makes everything worse.

So IMHO the best way to proceed is to fix the spacing issues in the
file once and for all. Contributors will stop propagating the bad
style when adding new bits to registers that already have bad style,
we will stop asking them to redo their patches and the CI emails will
become more relevant by having less semi-false errors.

Yes, there will be some pain involved for backporters, but at least
spacing issues like that are easy to spot and fix in the patch files.

This patch was generated by:

../../../../scripts/checkpatch.pl -f --strict --types SPACING \
	--fix-inplace i915_reg.h

I manually checked the output and everything seems sane.

v2: Single conflict around the addition of DP_TP_CTL_LINK_TRAIN_PAT4.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180618180943.894-1-paulo.r.zanoni@intel.com