ARM: dts: stm32mp: remove hnp-srp-disable for usbotg on dk1

Remove hnp-srp-disable for usbotg node because this feature is only needed
for usbotg in HOST mode (in drivers/usb/host/dwc2.c)
and this feature is not activated in stm32mp15 U-Boot
(stm32mp15_basic_defconfig and stm32mp15_trusted_defconfig);
only the device mode is activated and OTG is not supported in DWC2 driver.

This patch reduces the difference between U-Boot and Linux kernel
device-tree.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>