IAR compiler compatibility break in image.h

[Karambite]

Updated image.h to avoid breaking for IAR compiler.

#ifndef __packed
#define __packed __attribute__((__packed__))
#endif

This is a compatibility break with the IAR compiler. __packed is already a keyword that eliminates padding between members. This is not a definition, meaning it will always fall under the #ifndef. Any additions that use __packed will be replaced by the definition given.

I created a macro that will pack the structures based on the compiler used.

[nordicjm]

Commit needs a sign off and message text adding to commit i.e. git commit --amend -s then add description

[nordicjm]

@Karambite would you be able to fix this today or on Monday? Would like to pull latest changes into Zephyr with a manifest update soon

[Karambite]

@Karambite would you be able to fix this today or on Monday? Would like to pull latest changes into Zephyr with a manifest update soon

Sorry I haven't had time to get back to this. I will try to close this over the weekend

[Karambite]

I tried to rebase and accidentally closed this PR. A new one is opened here #2149.