m68k: emu: Remove unused vsnprintf() return value in nfprint()

m68k: emu: Remove unused vsnprintf() return value in nfprint()

When building with W=1:

    arch/m68k/emu/natfeat.c: In function ‘nfprint’:
    arch/m68k/emu/natfeat.c:59:13: warning: variable ‘n’ set but not used [-Wunused-but-set-variable]
       59 |         int n;
	  |             ^

As the return value of vsnprintf() is unused, and serves no practical
purpose here, fix this by removing the variable.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/a8b6b17ff352cc560d1848a92d171bb0f44ccb27.1694613528.git.geert@linux-m68k.org