The characters 0 to 9, *, # and + are accepted in the digit only mode of
GET INPUT/INKEY commands according to the 3GPP/ETSI standard, but only
numeric charactrers 0 to 9 are used in some actual use-cases. It must be
confusing to display all the allowed characters including *, # and + as
the helper text on the input screen in that case, so whether to display
the allowed characters must be configurable.
Bug: 128890104
Test: Confirmed the expected behavior in manual test cases.
Change-Id: I97ed3dd538c55f48eb05dad96e4836a48a295675
1c5203a65b