asm-tests/i386-pc: Check that movl is 5 bytes.

asm-tests/i386-pc: Check that movl is 5 bytes.

LLVM 3.9 now emits short form of jump instructions, but it is still using
32 bit addresses for some movl instructions. Fortunately it was caught early:

clang ... boot/i386/pc/boot.S
clang -cc1as: fatal error: error in backend: invalid .org offset '440' (at offset '441')

Add additional check to catch it during configure run and force -no-integrated-as.

Closes: 49200
More details in
  https://lists.gnu.org/archive/html/grub-devel/2015-02/msg00099.html
  https://llvm.org/bugs/show_bug.cgi?id=22662