elf, uapi: Remove struct tag 'dynamic'

Such a generic struct tag shouldn't have been exposed in a public
header.  Since it's undocumented, we can assume it's a historical
accident.  And since no software (at least on Debian) relies on this
tag, we can safely remove it.

Here are the results of a Debian Code Search[1]:

$ # packages that contain 'include [<"]linux/elf\.h[">]'
$ curl -s https://codesearch.debian.net/results/e5e7c74dfcdae609/packages.txt > include
$ # packages that contain '\bstruct dynamic\b'
$ curl -s https://codesearch.debian.net/results/b23577e099048c6a/packages.txt > struct
$ cat struct include | sort | uniq -d
chromium
hurd
linux
qemu
qt6-webengine
qtwebengine-opensource-src
$ # chromium: Seems to hold a copy of the UAPI header.  No uses of the tag.
$ # hurd:     Same thing as chromium.
$ # linux:    :)
$ # qemu:     Same thing as chromium.
$ # qt6-webengine:  Same thing as all.
$ # qtwebengine-opensource-src:  Yet another copy.

Link: https://codesearch.debian.net/ [1]
Link: https://lore.kernel.org/linux-mm/[email protected]/T/
Cc: "Eric W. Biederman" <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: David Howells <[email protected]>
Cc: Rolf Eike Beer <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Dave Jones <[email protected]>
Signed-off-by: Alejandro Colomar <[email protected]>
Signed-off-by: Kees Cook <[email protected]>

Author: alejandro-colomar

include/uapi/linux/elf.h

@@ -140,7 +140,7 @@ typedef __s64	Elf64_Sxword;
 #define ELF64_ST_BIND(x)	ELF_ST_BIND(x)
 #define ELF64_ST_TYPE(x)	ELF_ST_TYPE(x)
 
-typedef struct dynamic {
+typedef struct {
   Elf32_Sword d_tag;
   union {
     Elf32_Sword	d_val;