target/ppc: Filter mtmsr[d] input before setting MSR

target/ppc: Filter mtmsr[d] input before setting MSR

PowerISA says that mtmsr[d] "does not alter MSR[HV], MSR[S], MSR[ME], or
MSR[LE]", but the current code only filters the GPR-provided value if
L=1. This behavior caused some problems in FreeBSD, and a build option
was added to work around the issue [1], but it seems that the bug was
not reported in launchpad/gitlab. This patch address the issue in qemu,
so the option on FreeBSD should no longer be required.

[1] https://cgit.freebsd.org/src/commit/?id=4efb1ca7d2a44cfb33d7f9e18bd92f8d68dcfee0

Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Message-Id: <20211015181940.197982-1-matheus.ferst@eldorado.org.br>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>