testsuite: Adjust g++.dg/opt/devirt2.C on SPARC

testsuite: Adjust g++.dg/opt/devirt2.C on SPARC

Since 20231124, g++.dg/opt/devirt2.C began to FAIL on 32 and 64-bit
Solaris/SPARC:

FAIL: g++.dg/opt/devirt2.C  -std=gnu++14  scan-assembler-times (jmp|call)[^\\n]*xyzzy 4
FAIL: g++.dg/opt/devirt2.C  -std=gnu++17  scan-assembler-times (jmp|call)[^\\n]*xyzzy 4
FAIL: g++.dg/opt/devirt2.C  -std=gnu++20  scan-assembler-times (jmp|call)[^\\n]*xyzzy 4
FAIL: g++.dg/opt/devirt2.C  -std=gnu++98  scan-assembler-times (jmp|call)[^\\n]*xyzzy 4

This is no doubt due to

commit ba0869323e1d45b1328b4cb723cb139a2e2146c3
Author: Maciej W. Rozycki <macro@embecosm.com>
Date:   Thu Nov 23 16:13:59 2023 +0000

    testsuite: Fix subexpressions with `scan-assembler-times'

which fixes exactly the double-counting the test relied on/worked around
on sparc.  Fixed by adjusting the count.

Tested on sparc-sun-solaris2.11.

2023-11-28  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	gcc/testsuite:
	* g++.dg/opt/devirt2.C: Adjust scan-assembler-count on sparc for
	removal of -inline from regexp.  Update comment.