drivers: modem_if: replace mif P4 with mif P5 to fix l2_hsic issue

-reapply:
 drivers: modem_if: use memcpy in dpram_download for header
 https://github.com/pershoot/galaxy-31/commit/0dc15f580424db4d11928e0fcc1e72e081cba444#drivers/misc/modem_if