tools/nolibc: arm: use clang-compatible asm syntax

The clang assembler rejects the current syntax.
Switch to a syntax accepted by both GCC and clang.

Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20240807-nolibc-llvm-v2-1-c20f2f5fc7c2@weissschuh.net


Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>