target/ppc: Simplify powerpc_excp_booke

target/ppc: Simplify powerpc_excp_booke

Differences from the generic powerpc_excp code:

- No MSR bits are cleared at interrupt dispatch;
- No MSR_HV;
- No power saving states;
- No Hypervisor Emulation Assistance;
- SPEU needs special handling;
- Big endian only;
- Both 64 and 32 bits;
- No System call vectored;
- No Alternate Interrupt Location.

Exceptions used:

POWERPC_EXCP_ALIGN
POWERPC_EXCP_APU
POWERPC_EXCP_CRITICAL
POWERPC_EXCP_DEBUG
POWERPC_EXCP_DECR
POWERPC_EXCP_DSI
POWERPC_EXCP_DTLB
POWERPC_EXCP_EFPDI
POWERPC_EXCP_EFPRI
POWERPC_EXCP_EXTERNAL
POWERPC_EXCP_FIT
POWERPC_EXCP_FPU
POWERPC_EXCP_ISI
POWERPC_EXCP_ITLB
POWERPC_EXCP_MCHECK
POWERPC_EXCP_PROGRAM
POWERPC_EXCP_RESET
POWERPC_EXCP_SPEU
POWERPC_EXCP_SYSCALL
POWERPC_EXCP_WDT

Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Message-Id: <20220128224018.1228062-3-farosas@linux.ibm.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>