Revert "keyguard: dont show enter key when quick unlock is enabled"

This reverts commit 15d5dd41.

"But then you're giving out whether quick unlock is enabled or not,
effectively giving knowledge to someone, who picked up your device,
that they can brute-force the PIN without ever being locked out."

Effectively, this will lead to bruteforce attacks.

Change-Id: I87c1408348b009e3b2e4375b6e99e65d809de1ab