VAX: Fix invalid RTX operand access in `nonindexed_address_p'

VAX: Fix invalid RTX operand access in `nonindexed_address_p'

Replace an unguarded early access to the incoming RTX's operand 0 in
`nonindexed_address_p' with direct accesses at the actual use places,
fixing a libgcc build error:

during RTL pass: reload
.../libgcc/libgcc2.c: In function '__udiv_w_sdiv':
.../libgcc/libgcc2.c:649:1: internal compiler error: RTL check: expected elt 0 type 'e' or 'u', have 'r' (rtx reg) in nonindexed_address_p, at config/vax/vax.cc:1826

where `--enable-checking=rtl' has been specified so as to enable RTL
consistency checks.

	gcc/
	* config/vax/vax.cc (nonindexed_address_p): Move incoming RTX's
	operand 0 access to the actual use places.