target/ppc: fix exception error value in slbfee

target/ppc: fix exception error value in slbfee

Testing on a POWER9 DD2.3, we observed that the Linux kernel delivers a
signal with si_code ILL_PRVOPC (5) when a userspace application tries to
use slbfee. To obtain this behavior on linux-user, we should use
POWERPC_EXCP_PRIV with POWERPC_EXCP_PRIV_OPC.

No functional change is intended for softmmu targets as
gen_hvpriv_exception uses the same 'exception' argument
(POWERPC_EXCP_HV_EMU) for raise_exception_*, and the powerpc_excp_*
methods do not use lower bits of the exception error code when handling
POWERPC_EXCP_{INVAL,PRIV}.

Reported-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20220627141104.669152-3-matheus.ferst@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>