[platform][zynq] make sure the slcr is unlocked at the right spots during boot

For whatever reason the sequence worked out on zybo targets so that LVL_SHFTR_EN
was able to be set, but not on other targets.
[platform][zynq] print fpga clocks even if they're not enabled
[tools][lkboot] allow lkboot <host> :command to send 'raw' commands
[scripts][do-arm64] update virtual machine name for foundation host
[arm64] only save partial registers on irq entry

Patch by Vidya Sagar:
saves and restores only regs 0~17 as 18~30 are already
being saved in context switch API for irq and fiq
exceptions
[arch][x86-64] fix the default TOOLCHAIN_PATH setup

This was broken in a recent make file change by always setting
TOOLCHAIN_PREFIX in the wrapper makefile.
[lib][libc] fix floating point printf for negatives
[project][uzed-test] sync with zybo-test
[lib][minip] a bunch of tcp fixes

-add proper ref counting to facilitate sockets hanging around after tcp_close()
-add a bunch of more active and passive close transitions
-general bugfixes
-add 'tcp sockets' debug command to dump all of the active sockets
[lib][minip] optimize the net_timer to only run if there's a pending event

-add TIME_WAIT socket timeouts
-fix retransmit timeouts to work properly for the right states
-handle a few more socket states in tcp_close()
[tools][lkboot] dns lookup the host address on the command line
[minip] Correct ip ordering in status, add IPV4_SPLIT macro
gem wip: increment/wrap descriptors rather than using 0 & 1
[pktbuf] Fix NULL deref when the freelist is empty
WIP for noblock tx