x86/entry/64: Merge SAVE_C_REGS and SAVE_EXTRA_REGS, remove unused extensions

x86/entry/64: Merge SAVE_C_REGS and SAVE_EXTRA_REGS, remove unused extensions

All current code paths call SAVE_C_REGS and then immediately
SAVE_EXTRA_REGS. Therefore, merge these two macros and order the MOV
sequeneces properly.

While at it, remove the macros to save all except specific registers,
as these macros have been unused for a long time.

Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Dominik Brodowski <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>