[media] s5p_mfc: don't use an external symbol called 'debug'

The 'debug' name is known to cause conflicts with allyesconfig
on several archs. So, localize its name.

>> drivers/built-in.o:(.bss+0xc7ee2c): multiple definition of `debug'
   arch/x86/built-in.o:(.entry.text+0xf78): first defined here
   ld: Warning: size of symbol `debug' changed from 86 in arch/x86/built-in.o to 4 in drivers/built-in.o

While here, fix a wrong file name reference

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>