um: Replace __ASSEMBLY__ with __ASSEMBLER__ in the usermode headers

um: Replace __ASSEMBLY__ with __ASSEMBLER__ in the usermode headers

While the GCC and Clang compilers already define __ASSEMBLER__
automatically when compiling assembly code, __ASSEMBLY__ is a
macro that only gets defined by the Makefiles in the kernel.
This can be very confusing when switching between userspace
and kernelspace coding, so let's standardize on the __ASSEMBLER__
macro that is provided by the compilers now.

This is a completely mechanical patch (done with a simple "sed -i"
statement).

Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-um@lists.infradead.org
Signed-off-by: Thomas Huth <thuth@redhat.com>
Link: https://patch.msgid.link/20250314071013.1575167-36-thuth@redhat.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>