net: shell: Show also ISR and main stack usage
net: shell: Show also ISR and main stack usage

The "net stacks" command will also print main and interrupt
handler stack sizes.

Change-Id: I1b867be81ac8b4f6d9446f484ebb8b1d852b98b0
Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

fbsder/zephyr,fbsder/zephyr,fbsder/zephyr,fbsder/zephyr,fbsder/zephyr