Zephyr: Guybrush: Actually enable tab completion
Zephyr: Guybrush: Actually enable tab completion

Add the CONFIG_SHELL_TAB option to actually enable tab completion in the
shell.

BRANCH=None
BUG=None
TEST=load on guybrush and observe the wonder that is automatic tab
completion

Signed-off-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Change-Id: I8866fdfc60011570a45aa74944e1d88c48164cc4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3321391
Reviewed-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Commit-Queue: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec