boot: zephyr: add ram_load overlays for nrf52840dk and mimxrt1050_evk boards #2608

Job	Run time
config (RELEASE 2,4,6 SIGNATURE)	9m 9s
config (RELEASE 2,4,6 SIGNATURE LOW)	9m 21s
config (RELEASE 2,4,6 SIGNATURE MEDIUM)	9m 10s
config (RELEASE 8,10 SIGNATURE)	7m 14s
config (RELEASE 8,10 SIGNATURE LOW)	7m 16s
config (RELEASE 8,10 SIGNATURE MEDIUM)	7m 21s
config (MINSIZEREL 2,4,6 SIGNATURE)	9m 30s
config (MINSIZEREL 2,4,6 SIGNATURE LOW)	9m 27s
config (MINSIZEREL 2,4,6 SIGNATURE MEDIUM)	9m 21s
config (MINSIZEREL 8,10 SIGNATURE)	7m 32s
config (MINSIZEREL 8,10 SIGNATURE LOW)	7m 30s
config (MINSIZEREL 8,10 SIGNATURE MEDIUM)	7m 25s
	1h 40m 16s

Provide feedback