Patch by Rohit Seth, Fengua Yu, and Arun Sharma:

Please find attached a patch for kernel entry exit optimization. This is
based on 2.5.69 kernel.

The main items covered by this patch are:
1) Support for 16 bytes instructions as per SDM2.1 (CSD/SSD in pt_regs)
2) f10-f11 are added as additional scratch registers for kernel's use.
3) Re-arrange pt_regs to access less cache lines in system call. Reduce
scratch register saving/restoring in system call path.
4) A few instruction reorg in low-level code.