counter: microchip-tcb-capture: Allow shared IRQ for multi-channel TCBs

counter: microchip-tcb-capture: Allow shared IRQ for multi-channel TCBs

Mark the interrupt as IRQF_SHARED to permit multiple counter channels to
share the same TCB IRQ line.

Each Timer/Counter Block (TCB) instance shares a single IRQ line among its
three internal channels. When multiple counter channels (e.g., counter@0
and counter@1) within the same TCB are enabled, the second call to
devm_request_irq() fails because the IRQ line is already requested by the
first channel.

Cc: stable@vger.kernel.org
Fixes: e5d581396821 ("counter: microchip-tcb-capture: Add IRQ handling")
Signed-off-by: Dharma Balasubiramani <dharma.b@microchip.com>
Reviewed-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
Reviewed-by: Bence Csókás <bence98@sch.bme.hu>
Link: https://lore.kernel.org/r/20251006-microchip-tcb-v1-1-09c19181bb4a@microchip.com
Signed-off-by: William Breathitt Gray <wbg@kernel.org>