This patch makes possible to choose custom byte which should be used
to enable non-permanent readout protection (RDP1). Actually, any byte
except 0xAA and 0xCC (which are used by RDP0 and RDP2 respectively)
can be used to enable RDP1 but in multi-image environment, some other
image could check if RDP1 is enabled by comparing it to some hardcoded
value.
If property is not defined, 0x55 will be used to enable RDP1. The
default value comes from STM32 HAL.
Signed-off-by: Patryk Duda <pdk@semihalf.com>
