dt-bindings: serial: brcm,bcm7271-uart: Constrain clocks

dt-bindings: serial: brcm,bcm7271-uart: Constrain clocks

Lists should have fixed constraints, because binding must be specific in
respect to hardware, thus add missing constraints to number of clocks.

Cc: stable <stable@kernel.org>
Fixes: 88a499cd70d4 ("dt-bindings: Add support for the Broadcom UART driver")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250812121630.67072-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>