MIPS: math-emu: Add FP emu debugfs clear functionality

MIPS: math-emu: Add FP emu debugfs clear functionality

Add capability for the user to clear all FP emu debugfs counters.

This is achieved by having a special debugfs file "fpuemustats_clear"
(under default location "/sys/kernel/debug/mips"). Each access to the
file results in setting all counters to zero (it is enough, let's say,
to issue a "cat /sys/kernel/debug/mips/fpuemustats_clear").

This functionality already exists for R2 emulation statistics,
but was missing for FP emulation statistics. The implementation in
this patch is consistent with its R2 emulation counterpart.

Signed-off-by: Miodrag Dinic <[email protected]>
Signed-off-by: Goran Ferenc <[email protected]>
Signed-off-by: Aleksandar Markovic <[email protected]>
Cc: Douglas Leung <[email protected]>
Cc: James Hogan <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Petar Jovanovic <[email protected]>
Cc: Raghu Gandham <[email protected]>
Cc: [email protected]
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/17144/
Signed-off-by: Ralf Baechle <[email protected]>