doc: efi_loader: Tidy up the bootefi-command docs

There are backslashes in some of the tags which seems to be unnecessary.
Remove then.

Change the word 'either' to 'any' since there are three options.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
1 file changed