docs: integration: document need for 'unsquashfs' tool for 'rauc info'
docs: integration: document need for 'unsquashfs' tool for 'rauc info'

Suggested-by: e07f266e99af6c8d987ab67f2c1df1bd98d961a1@i2se.com
Signed-off-by: Enrico Jorns <a2e5f936c390f36494e46e71bcfbe365bb1e8c49@pengutronix.de>

jluebbe/rauc,ejoerns/rauc,rauc/rauc,ejoerns/rauc,jluebbe/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc,rauc/rauc