irqchip: Use int type to store negative error codes

Change the 'ret' variable from unsigned int to int to store negative error
codes or zero returned by other functions.

Storing the negative error codes in unsigned type, doesn't cause an issue
at runtime but assigning negative error codes to unsigned type may trigger
a compiler warning when the -Wsign-conversion flag is enabled.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/all/20250829132020.82077-1-rongqianfeng@vivo.com