Fix MIPS BR2_PACKAGE_LINUX_TOOLS_GPIO build

Update mips for snapshot and initrd features.

Document MIPS limitations.

Improve description of test procedure

README.adoc

@@ -910,6 +910,16 @@ no module object found for ''
 ./build -a mips64
 ....
 
+Keep in mind that MIPS has the worst support our architectures due to the smaller community. Patches welcome as usual.
+
+TODOs:
+
+* networking is not working. See also:
+** https://stackoverflow.com/questions/21496449/networking-is-not-working-on-qemu-guest-malta-mips
+** https://unix.stackexchange.com/questions/208266/setting-up-qemu-and-mipsel-networking-trouble
+** https://unix.stackexchange.com/questions/354127/qemu-mips-and-debian
+* <<gdb>> does not work properly, does not find `start_kernel`
+
 === init
 
 When the Linux kernel finishes booting, it runs an executable as the first and only userland process.
@@ -1548,7 +1558,7 @@ Related: https://stackoverflow.com/questions/6405083/initrd-and-booting-the-linu
 
 ==== initramfs
 
-initramfs is just like initrd, but you also glue the image directly to the kernel image itself.
+initramfs is just like <<initrd>>, but you also glue the image directly to the kernel image itself.
 
 So the only argument that QEMU needs is the `-kernel`, no `-drive` not even `-initrd`! Pretty cool.
 
@@ -1710,7 +1720,7 @@ You can then restore CPU, memory and disk state back at any time.
 
 qcow2 filesystems must be used for that to work.
 
-To test it out, login into the VM, and run:
+To test it out, login into the VM with and run:
 
 ....
 /count.sh
@@ -1764,6 +1774,8 @@ cat f
 
 And the output is `0`.
 
+Our setup does not allow for snapshotting while using <<initrd>>.
+
 == Failed action
 
 === Record and replay