m68k: fix typo

otherwise you get compile warnings, when building for m68k.

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/sysdeps/linux/m68k/bits/huge_vall.h

@@ -26,7 +26,7 @@
 # define HUGE_VALL	(__builtin_huge_vall ())
 #elif __GNUC_PREREQ(2,96)
 # define HUGE_VALL	(__extension__ 0x1.0p32767L)
-#elif defined__GNUC__
+#elif defined __GNUC__
 
 # define HUGE_VALL					\
   (__extension__					\