bootutil: Fix for flash_area_id_to_image #1455

Job	Run time
environment (esp32, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secureb...	2m 42s
environment (esp32, serialrecovery)	2m 9s
environment (esp32s2, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	2m 28s
environment (esp32s2, serialrecovery)	2m 16s
environment (esp32s3, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	2m 27s
environment (esp32s3, serialrecovery)	2m 7s
environment (esp32c3, secureboot-sign-rsa2048,secureboot-sign-rsa3072,secureboot-sign-ec256,secur...	2m 4s
environment (esp32c3, serialrecovery)	1m 50s
environment (esp32, multi-image,multi-boot, multi)	1m 59s
environment (esp32s3, multi-image,multi-boot, multi)	1m 49s
	21m 51s

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