Nami: Add host command handler for keyboard backlight control
Nami: Add host command handler for keyboard backlight control

This patch adds host command handlers for
EC_CMD_PWM_SET_KEYBOARD_BACKLIGHT and CMD_PWM_GET_KEYBOARD_BACKLIGHT.

Signed-off-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>

BUG=b:74176833
BRANCH=none
TEST=Verify ectool pwmsetkblight works. Verify kblight console command
returns the value set by ectool and vice versa.

Change-Id: I1929c6a3772ab22cb4b3c68638da23aa23727596
Reviewed-on: https://chromium-review.googlesource.com/1022961
Commit-Ready: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Tested-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Reviewed-by: Aaron Durbin <af0622ab041e8b0f8e5819838dcc93898196e71f@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec