fallthrough pseudo-keyword macro conversions for 5.9-rc2

Hi Linus,

Please, pull the following tree-wide patch that replaces tons (2504) of
/* fall through */ comments, and its variants, with the new pseudo-keyword
macro fallthrough[1]. Also, remove unnecessary fall-through markings when
it is the case.

There are currently 1156 intances of this fallthrough pseudo-keyword
macro in mainline (5.9-rc1), that have been introduced over the last
couple of development cycles:

$ git grep -nw 'fallthrough;' | wc -l
1156

The global adoption of the fallthrough pseudo-keyword is something certain
to happen; so, better sooner than later. :) This will also save everybody's
time and thousands of lines of unnecessarily repetitive changelog text.

After applying this patch on top of 5.9-rc1, we'll have a total of 3660
instances of this macro:

$ git grep -nw 'fallthrough;' | wc -l
3660

This treewide patch doesn't address ALL fall-through markings in all
subsystems at once because I have previously sent out patches for some of
such subsystems separately, and I will follow up on them; however, this
definitely contributes most of the work needed to replace all the
fall-through markings with the fallthrough pseudo-keyword macro in the
whole codebase.

I have build-tested this patch on 10 different architectures: x86_64, i386,
arm64, powerpc, s390, sparc64, sh, m68k, powerpc64 and alpha (allyesconfig
for all of them). This is in linux-next already and kernel test robot has
also helped me to successfully build-test early versions of this
patch[2][3][4].

Thanks
--
[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
[2] https://lore.kernel.org/lkml/5f3cc99a.HgvOW3rH0mD0RmkM%25lkp@intel.com/
[3] https://lore.kernel.org/lkml/5f3dd1d2.l1axczH+t4hMBZ63%25lkp@intel.com/
[4] https://lore.kernel.org/lkml/5f3e977a.mwYHUIObbR4SHr0B%25lkp@intel.com/
treewide: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
1151 files changed