target/ppc: fix PMU Group A register read/write exceptions

target/ppc: fix PMU Group A register read/write exceptions

A call to "gen_(hv)priv_exception" should use POWERPC_EXCP_PRIV_* as the
'error' argument instead of POWERPC_EXCP_INVAL_*, and POWERPC_EXCP_FU is
an exception type, not an exception error code. To correctly set
FSCR[IC], we should raise Facility Unavailable with this exception type
and IC value as the error code.

Fixes: 565cb1096733 ("target/ppc: add user read/write functions for MMCR0")
Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20220627141104.669152-6-matheus.ferst@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>