[TF-M] Hotfix for GNUARM linker script

Hi all,

I uploaded a hotfix to fix a issue in GNUARM linker script. https://review.trustedfirmware.org/c/trusted-firmware-m/+/2767

The XXX_ATTR_FN label is named as XXX_LD_ATTR_FN for Application RoT Secure Partitions in GNUARM linker script. Thus GNUARM cannot get the dedicated section address to place the XXX_ATTR_FN section defined in the source code. It may cause linking error and crash during running.

Please help review the patch. Any comment is welcome and will speed up the fix. Thank you.

Best regards, Hu Ziji