gcc.dg/intmax_t-1.c compiles without error on VxWorks 7 SR06x0

This test currently fails on VxWorks 7 SR06x0 targets when in kernel
mode, because it expects a discrepancy between built-in and system
intmax_t for all VxWorks targets when in kernel mode.  Fortunately,
this has now been fixed when targetting VxWorks 7 SR06x0, so this
commit adjusts the "dg-error" condition to exclude newer versions of
VxWorks 7.

for  gcc/testsuite/ChangeLog

	* gcc.dg/intmax_t-1.c: Do not expect an error on *-*-vxworks7r*
	targets.