target/ppc: Simplify powerpc_excp_books

target/ppc: Simplify powerpc_excp_books

Differences from the generic powerpc_excp code:

- Not BookE, so some MSR bits are cleared at interrupt dispatch;
- Always uses HV_EMU if the CPU has MSR_HV;
- Exceptions always delivered in 64 bit.

Exceptions used:

POWERPC_EXCP_ALIGN
POWERPC_EXCP_DECR
POWERPC_EXCP_DSEG
POWERPC_EXCP_DSI
POWERPC_EXCP_EXTERNAL
POWERPC_EXCP_FPU
POWERPC_EXCP_FU
POWERPC_EXCP_HDECR
POWERPC_EXCP_HDSI
POWERPC_EXCP_HISI
POWERPC_EXCP_HVIRT
POWERPC_EXCP_HV_EMU
POWERPC_EXCP_HV_FU
POWERPC_EXCP_ISEG
POWERPC_EXCP_ISI
POWERPC_EXCP_MAINT
POWERPC_EXCP_MCHECK
POWERPC_EXCP_PERFM
POWERPC_EXCP_PROGRAM
POWERPC_EXCP_RESET
POWERPC_EXCP_SDOOR_HV
POWERPC_EXCP_SYSCALL
POWERPC_EXCP_SYSCALL_VECTORED
POWERPC_EXCP_THERM
POWERPC_EXCP_TRACE
POWERPC_EXCP_VPU
POWERPC_EXCP_VPUA
POWERPC_EXCP_VSXU

POWERPC_EXCP_HV_MAINT
POWERPC_EXCP_SDOOR

(I added the two above that were not being considered. They used to be
"Invalid exception". Now they become "Unimplemented exception" which
is more accurate.)

Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220124184605.999353-3-farosas@linux.ibm.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>