zephyr: Fix image encryption configuration for mbedTLS. #14

Job	Run time
environment (esp32, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secureb...	1m 41s
environment (esp32, serialrecovery)	1m 31s
environment (esp32s2, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	1m 39s
environment (esp32s2, serialrecovery)	1m 22s
environment (esp32s3, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	1m 42s
environment (esp32s3, serialrecovery)	1m 24s
environment (esp32c3, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	1m 39s
environment (esp32c3, serialrecovery)	1m 25s
environment (esp32, multi-image,multi-boot, multi)	1m 29s
environment (esp32s3, multi-image,multi-boot, multi)	1m 36s
	15m 28s

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