MIPS: math-emu: Reuse name array in debugfs_fpuemu()

MIPS: math-emu: Reuse name array in debugfs_fpuemu()

The FPU_STAT_CREATE_EX() macro used 114 times in debugfs_fpuemu()
declares a 32 byte char array to hold the name of a debugfs file. Since
each use of the macro declares a new char array out of the scope of all
the other uses, we end up with an unnecessarily large stack frame of
3648 bytes (ie. 114*32) plus the size of 2 pointers
(fpuemu_debugfs_base_dir & fpuemu_debugfs_inst_dir). This is enough to
trigger the frame size warnings from GCC in common configurations.

Avoid the unnecessary stack bloat by using a single name char array
which each usage of FPU_STAT_CREATE_EX() will reinitialize via the
strcpy() in adjust_instruction_counter_name().

Signed-off-by: Paul Burton <paulburton@kernel.org>
Reported-by: kbuild test robot <lkp@intel.com>
URL: https://lore.kernel.org/linux-mips/201911090929.xvXYuHUz%25lkp@intel.com/