cleanup: make get_syscall_args.c files more readable

cleanup: make get_syscall_args.c files more readable

Make get_syscall_args.c files more self-contained.  While they are
still being included by syscall.c, the latter no longer defines
get_syscall_args function.

* linux/aarch64/get_syscall_args.c: Include "arm/get_syscall_args.c"
with get_syscall_args temporarily defined to arm_get_syscall_args.
(get_syscall_args): Define.
* linux/alpha/get_syscall_args.c (get_syscall_args): Define.
* linux/arc/get_syscall_args.c: Likewise.
* linux/arm/get_syscall_args.c: Likewise.
* linux/avr32/get_syscall_args.c: Likewise.
* linux/bfin/get_syscall_args.c: Likewise.
* linux/crisv10/get_syscall_args.c: Likewise.
* linux/hppa/get_syscall_args.c: Likewise.
* linux/i386/get_syscall_args.c: Likewise.
* linux/ia64/get_syscall_args.c: Likewise.
* linux/m68k/get_syscall_args.c: Likewise.
* linux/metag/get_syscall_args.c: Likewise.
* linux/microblaze/get_syscall_args.c: Likewise.
* linux/mips/get_syscall_args.c: Likewise.
* linux/nios2/get_syscall_args.c: Likewise.
* linux/or1k/get_syscall_args.c: Likewise.
* linux/powerpc/get_syscall_args.c: Likewise.
* linux/s390/get_syscall_args.c: Likewise.
* linux/sh/get_syscall_args.c: Likewise.
* linux/sh64/get_syscall_args.c: Likewise.
* linux/sparc/get_syscall_args.c: Likewise.
* linux/tile/get_syscall_args.c: Likewise.
* linux/x86_64/get_syscall_args.c: Likewise.
* linux/xtensa/get_syscall_args.c: Likewise.
* syscall.c (get_syscall_args): Remove.
Include "get_syscall_args.c" in file scope.

Requested-by: Denys Vlasenko <dvlasenk@redhat.com>