mm: remove legacy install_special_mapping() code

All relevant architectures had already been converted to the new interface
(which just has an underscore in front of the name - not very imaginative
naming), this just force-converts the stragglers.

The modern interface is almost identical to the old one, except instead of
the page pointer it takes a "struct vm_special_mapping" that describes the
mapping (and contains the page pointer as one member), and it returns the
resulting 'vma' instead of just the error code.

Getting rid of the old interface also gets rid of some special casing,
which had caused problems with the mremap extensions to "struct
vm_special_mapping".

[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/CAHk-=whvR+z=0=0gzgdfUiK70JTa-=+9vxD-4T=3BagXR6dciA@mail.gmail.comTested-by: Rob Landley <rob@landley.net> # arch/sh/
Link: https://lore.kernel.org/all/20240819195120.GA1113263@thelio-3990X/


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Brian Cain <bcain@quicinc.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Jeff Xu <jeffxu@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Rob Landley <rob@landley.net>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>