extract and use FILE_LINE macro

Extract nifty FILE_LINE useful for printk style debugging:

	printk("%s\n", FILE_LINE);

It should not be used en mass probably because __FILE__ string literals
can be merged while FILE_LINE's won't. But for debugging it is what
the doctor ordered.

Don't add leading and trailing underscores, they're painful to type. 
Trust me, I've tried both versions.

Link: https://lkml.kernel.org/r/ebf12ac4-5a61-4b12-b8b0-1253eb371332@p183


Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>