TIM2_ETR not work on PE15

[yermin2]

My board (STM32MP135D) useTIM2 to count the external clock.

PE15 cannot work properly, but PA15 works normally.

	// ok
	tim2_pins_mx: tim2_mx-0 {
		pins {
			pinmux = <STM32_PINMUX('A', 15, AF1)>; /* TIM2_ETR */
		};
	};

	// not work
	tim2_pins_mx: tim2_mx-0 {
		pins {
			pinmux = <STM32_PINMUX('E', 15, AF1)>; /* TIM2_ETR */
		};
	};