Description: x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
References:
Notes:
 carnil> Introduced in fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow
 carnil> mitigation"). Vulnerable versions: 5.10.189 5.15.125 6.1.44 6.4.9 6.5-rc6.
Bugs:
upstream: released (6.6-rc3) [01b057b2f4cc2d905a0bd92195657dbd9a7005ab]
6.7-upstream-stable: N/A "Fixed before branching point"
6.6-upstream-stable: N/A "Fixed before branching point"
6.1-upstream-stable: released (6.1.56) [adbcec23c8423e3d5df1839c5ae91599dcf703cb]
5.10-upstream-stable: released (5.10.198) [ae806c74c0634b0c23855066d8ba28d850fd1260]
4.19-upstream-stable: N/A "Vulnerable code not present"
sid: released (6.5.6-1)
6.1-bookworm-security: released (6.1.64-1)
5.10-bullseye-security: released (5.10.205-1)
4.19-buster-security: N/A "Vulnerable code not present"