libsframe: testsuite: fix PR libsframe/33140

Commit 0d4d5a2633f missed some necessary adjustments to the testcase
after rebase.  SFrame FDE function start address data is now an offset
in PCREL encoding; reflect with a new flag SFRAME_F_FDE_START_ADDR_PCREL
in the header.

Adjust the newly added testcase.

PR libsframe/33140 SFrame test failures on x86-64

libsframe/testsuite/
	* libsframe.find/plt-findfre-2.c: Adjust for the new FDE func
	start addr encoding.