Fix image len bound check in update_ram.c

[danielinux]

Fixes Fenrir/228

[Copilot]

Pull request overview

Adds a missing bounds check to RAM-boot image loading to reject oversized images and extends the unit test suite to cover invalid headers, oversize rejection, and a successful RAM-boot path. This aligns wolfBoot_ramboot() behavior with existing fixed-partition size constraints used elsewhere in the image handling code.

Changes:

• Add a partition-size-based upper bound check for the image payload length in wolfBoot_ramboot().
• Add unit tests for RAM-boot: invalid magic, oversized length rejection, and success case.
• Register the new tests in the unit test suite runner.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/update_ram.c	Rejects images whose header-advertised payload size exceeds WOLFBOOT_PARTITION_SIZE - IMAGE_HEADER_SIZE before reading into RAM.
tools/unit-tests/unit-update-ram.c	Adds and registers coverage for RAM-boot failure/success paths (invalid header, oversize, success).

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