x86/entry/64/compat: Save one instruction in entry_INT80_compat()

x86/entry/64/compat: Save one instruction in entry_INT80_compat()

As %rdi is never user except in the following push, there is no
need to restore %rdi to the original value.

Signed-off-by: Dominik Brodowski <[email protected]>
Acked-by: Linus Torvalds <[email protected]>
Acked-by: 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]
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>