hw/arm/aspeed: Export and rename create_pca9552() for reuse

hw/arm/aspeed: Export and rename create_pca9552() for reuse

The helper function create_pca9552() has been renamed to
aspeed_create_pca9552() and made non-static for reuse by other Aspeed
machine source files. A corresponding prototype is now declared in
aspeed.h.

This allows multiple Aspeed platforms to share PCA9552 I2C LED controller
initialization logic, improving code reuse and reducing duplication.

No functional changes.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20251104031325.146374-4-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>