mips: use PTRACE_GETREGS to fetch all registers

* linux/mips/arch_regs.h (struct mips_regs): New structure.
(mips_REG_*): New macros.
* signal.c (sys_sigreturn) [MIPS]: Use mips_REG_SP.
* syscall.c [MIPS] (struct mips_regs): New variable.
[MIPS] (ARCH_REGS_FOR_GETREGS): New macro.
(mips_a3, mips_r2): Remove.
(print_pc) [MIPS]: Use mips_REG_EPC.
(get_scno) [MIPS]: Use mips_REG_V0 and mips_REG_A3.
(get_syscall_args) [MIPS]: Use mips_REG_A[0-5].
(get_syscall_result) [MIPS]: Remove.
(get_error) [MIPS]: Use mips_REG_A3 and mips_REG_V0.
3 files changed