two more objtool warnings: lib/ubsan.o and fs/fs_pin.o

[Arnd Bergmann]

Hi Josh,

I ran into two more warnings with the two patches you sent me in private,
using gcc-7.1.1:

lib/ubsan.o: warning: objtool: val_to_string.constprop.7()+0x97: leave
instruction with modified stack frame
.config: https://pastebin.com/dl/g04Dwdwx

fs/fs_pin.o: warning: objtool: pin_kill()+0x139: stack state mismatch:
cfa1=7+88 cfa2=7+96
.config: https://pastebin.com/dl/6gK6MadB

I assume you are faster at analysing than me, so I have not tried to get
to the bottom of these at all. Let me know if you need help reproducing
the warnings. It's also possible that they are fixed by some other patches
that you already sent but that are not in linux-next yet.

       Arnd