MIPS/LD/testsuite: Adapt VxWorks segment matching for PR ld/20815 fix

Adjust segment addresses in the program header dump to account for the
inclusion of the program headers in the segment, removing a regression
from commit 1a9ccd70f9a7 ("Fix the linker so that it will not silently
generate ELF binaries with invalid program headers.  Fix readelf to
report such invalid binaries."):

mips-vxworks  -FAIL: VxWorks executable test 2 (dynamic)
mipsel-vxworks  -FAIL: VxWorks executable test 2 (dynamic)