pad: drop the custom mapping code again

Jason will fix this upstream so we don't have to care about KEY_PROG1..3
23 jobs for wip/tablet-pad-keys in 2 minutes and 58 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Container Prep
passed #390563
arch:rolling@container-prep

00:00:19

passed #390560
fedora:29@container-prep

00:00:22

passed #390559
fedora:30@container-prep

00:00:22

passed #390564
freebsd:11.2@container-prep

00:00:30

passed #390561
ubuntu:18.10@container-prep

00:00:20

passed #390562
ubuntu:19.04@container-prep

00:00:23

 
  Build
passed #390580
arch:rolling@default-build

00:01:25

passed #390565
fedora:29@default-build

00:01:23

passed #390573
fedora:30@build-no-debuggui

00:01:16

passed #390574
fedora:30@build-no-debuggui-nodeps

00:01:17

passed #390571
fedora:30@build-no-docs

00:01:11

passed #390572
fedora:30@build-no-docs-nodeps

00:01:10

passed #390569
fedora:30@build-no-libwacom

00:01:21

passed #390570
fedora:30@build-no-libwacom-nodeps

00:01:21

passed #390575
fedora:30@build-no-tests

00:01:16

passed #390576
fedora:30@build-no-tests-nodeps

00:01:23

passed #390566
fedora:30@default-build

00:01:19

passed #390567
fedora:30@default-build-release

00:00:33

passed #390568
fedora:30@scan-build

00:02:25

passed #390577
fedora:30@valgrind

00:01:16

passed #390581
freebsd:11.2@default-build

00:00:17

passed #390578
ubuntu:18.10@default-build

00:01:14

passed #390579
ubuntu:19.04@default-build

00:01:24