checkkconfigsymbols.py: support Kconfig's 'imply' statement

Support the new imply statement in Kconfig. The imply statement has
been added by commit 237e3ad0f195 ("Kconfig: Introduce the "imply"
keyword") and is a weak version of a select, but the target symbol can
still be turned off.

Signed-off-by: Andreas Ziegler <[e-mail]>
Signed-off-by: Valentin Rothberg <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

scripts/checkkconfigsymbols.py

···
 DEF = r"^\s*(?:menu){,1}config\s+(" + SYMBOL + r")\s*"
 EXPR = r"(?:" + OPERATORS + r"|\s|" + SYMBOL + r")+"
 DEFAULT = r"default\s+.*?(?:if\s.+){,1}"
-STMT = r"^\s*(?:if|select|depends\s+on|(?:" + DEFAULT + r"))\s+" + EXPR
+STMT = r"^\s*(?:if|select|imply|depends\s+on|(?:" + DEFAULT + r"))\s+" + EXPR
 SOURCE_SYMBOL = r"(?:\W|\b)+[D]{,1}CONFIG_(" + SYMBOL + r")"
 
 # regex objects