target/ppc: Fix MPCxxx FPU interrupt address

target/ppc: Fix MPCxxx FPU interrupt address

The Floating-point Unavailable and Decrementer interrupts are being
registered at the same 0x900 address. The FPU should be at 0x800
instead.

Verified on MPC555, MPC860 and MPC885 user manuals.

Reported-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20211208123029.2052625-2-farosas@linux.ibm.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>