newlib: libc: update asmdefs.h compatible with Cygwin AArch64

 newlib: libc: update asmdefs.h compatible with Cygwin AArch64
 
 This patch synchronizes newlib/libc/machine/aarch64/asmdefs.h header with
 version from https://github.com/ARM-software/optimized-routines/commit/4352245388a55a836f3ac9ac5907022c24ab8e4c
 commit that added support for AArch64 Cygwin.
 
 This version of the header removed PTR_ARG and SIZE_ARG macros as ILP32 was
 deprecated which introduced changes in many .S files so the patch contains
 removal of usages of those macros.
 
 On top of that, setjmp.S and rawmemchr.S were refactored to use
 ENTRY/ENTRY_ALIGN and END macros.                                         `
 
 Signed-off-by: Radek Bartoň <radek.barton@microsoft.com>