Sierra Wireless EM7305: support ICCID response without !

[MarSoft]

On my modem, AT!ICCID? command gives response without a preceding !:

AT!ICCID?
ICCID: 8970162010103256136

OK

Without this fix, I get the following repeated error in ModemManager logs:

Dec 06 00:47:39 dook ModemManager[107911]: <msg> [modem24] power state updated: on
Dec 06 00:47:39 dook ModemManager[107911]: <wrn> [modem24] could not load SIM identifier: ICCID response contained invalid character 'I' at index '0' (3 retries left)
Dec 06 00:47:41 dook ModemManager[107911]: <wrn> [modem24] could not load SIM identifier: ICCID response contained invalid character 'I' at index '0' (2 retries left)
Dec 06 00:47:42 dook ModemManager[107911]: <wrn> [modem24] could not load SIM identifier: ICCID response contained invalid character 'I' at index '0' (1 retries left)
Dec 06 00:47:43 dook ModemManager[107911]: <wrn> [modem24] could not load SIM identifier: ICCID response contained invalid character 'I' at index '0'
Dec 06 00:47:43 dook ModemManager[107911]: <msg> [modem24] 3GPP registration state changed (unknown -> denied)
Dec 06 00:47:43 dook ModemManager[107911]: <msg> [modem24] 3GPP packet service state changed (unknown -> detached)