Upgrade to lwIP 2.2.1

[mitchellwaite]

Who doesn't love an upgrade to a modern version of a dependency? Here we've got lwIP 2.2.1 (Released Feb 6, 2025).... 1.4.1 was released in ~2012 or so (14 years ago)

Main changes (other than replacing the lwip sources) are as follows:

• Makefile was updated to include the correct set of lwip object files, and make the install command happy by creating the proper directory structure. There were some changes to the source files in newer versions of lwip
• sys_check_timeouts() was fixed, so we don't need to manually check and fire each timer (of which there are more to worry about in LWIP 2.2.1)
• netif_set_link_up and netif_set_up are called in the appropriate places, lwip < 1.4.1 is more strict about the interface being up before it will transmit packets
• types provided by stdint.h were removed from cc.h
• console "waiting for DHCP" message was updated so we don't print as many dots to the screen, rather we flash a dot while waiting. DHCP init takes a bit longer in 2.2.1

NOTE: Free60Project/xell-reloaded#35 is a prerequisite to this for XeLL, commit Free60Project/xell-reloaded@9c357a7 contains an update to tftp.c that resolves compile issues and allows it to compile on both 1.4.1 and 2.2.1

ELF for testing:
xenon.elf.zip