x86/idle: Remove CONFIG_AS_TPAUSE

There is not much point in CONFIG_AS_TPAUSE at all when the emitted
assembly is always the same - it only obfuscates the __tpause() code
in essence.

Remove the TPAUSE insn mnemonic from __tpause() and leave only
the equivalent byte-wise definition. This can then be changed
back to insn mnemonic once binutils 2.31.1 is the minimum version
to build the kernel. (Right now it's 2.25.)

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250402180827.3762-4-ubizjak@gmail.com