hw/intc/aspeed: Support setting different memory size

hw/intc/aspeed: Support setting different memory size

According to the AST2700 datasheet, the INTC(CPU DIE) controller has 16KB
(0x4000) of register space, and the INTCIO (I/O DIE) controller has 1KB (0x400)
of register space.

Introduced a new class attribute "mem_size" to set different memory sizes for
the INTC models in AST2700.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250307035945.3698802-2-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>