MSP430: Skip index-1.c test

To access the "n - 100000"th element of "a" in this test, GCC will
generate the following code for msp430-elf with -mcpu=msp430x:

  RLAM.W  #1, R12
  MOV.W a-3392(R12), R12

Since there aren't actually 100,000 elements in a, this means that
"a-3392" offset calculated by the linker can overflow, as the address of
"a" can validly be less than 3392.

The relocations used for -mcpu=msp430 and -mlarge are not as strict and
the calculated value is allowed to wrap around the address space,
avoiding relocation overflows.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/execute/index-1.c: Skip for the default MSP430 430X ISA.