elfcore: correct reference to CONFIG_UML

Commit 6e7b64b9dd6d ("elfcore: fix building with clang") introduces
special handling for two architectures, ia64 and User Mode Linux.
However, the wrong name, i.e., CONFIG_UM, for the intended Kconfig
symbol for User-Mode Linux was used.

Although the directory for User Mode Linux is ./arch/um; the Kconfig
symbol for this architecture is called CONFIG_UML.

Luckily, ./scripts/checkkconfigsymbols.py warns on non-existing configs:

  Referencing files: include/linux/elfcore.h
  Similar symbols: UML, NUMA

Correct the name of the config to the intended one.

[akpm@linux-foundation.org: fix um/x86_64, per Catalin]
  Link: https://lkml.kernel.org/r/20211006181119.2851441-1-catalin.marinas@arm.com
  Link: https://lkml.kernel.org/r/YV6pejGzLy5ppEpt@arm.com

Link: https://lkml.kernel.org/r/20211006082209.417-1-lukas.bulwahn@gmail.com
Fixes: 6e7b64b9dd6d ("elfcore: fix building with clang")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Barret Rhoden <brho@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/elfcore.h b/include/linux/elfcore.h
index 2aaa157..957ebec 100644
--- a/include/linux/elfcore.h
+++ b/include/linux/elfcore.h
@@ -109,7 +109,7 @@
-#if defined(CONFIG_UM) || defined(CONFIG_IA64)
+#if (defined(CONFIG_UML) && defined(CONFIG_X86_32)) || defined(CONFIG_IA64)
  * These functions parameterize elf_core_dump in fs/binfmt_elf.c to write out
  * extra segments containing the gate DSO contents.  Dumping its