C-SKY: remove user_regs definition

C-SKY GDB dose not use this file for ptrace and coredump.  ptrace can use
pt_regs definition from linux kernel directly.  The old definition only
got 34 regs instead of 38 regs from linux kernel, which will corrupted
the memory after ptrace PTRACE_GETREGSET call.

	* sysdeps/unix/sysv/linux/csky/sys/procfs.h: Use linux definition
	directly.
	* sysdeps/unix/sysv/linux/csky/sys/user.h: Remove user_regs
	definition.