.gitlab-ci.yml: update after adding bananapi_m2_plus_defconfig

Commit cef57c964284f9b545a2347dd6eb1654e03dfd6e added
bananapi_m2_plus_defconfig but forgot to update .gitlab-ci.yml. Do it
now.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

.gitlab-ci.yml

@@ -87,6 +87,7 @@ atmel_sama5d4_xplained_defconfig: *defconfig
 atmel_sama5d4_xplained_dev_defconfig: *defconfig
 atmel_sama5d4_xplained_mmc_defconfig: *defconfig
 atmel_sama5d4_xplained_mmc_dev_defconfig: *defconfig
+bananapi_m2_plus_defconfig: *defconfig
 bananapro_defconfig: *defconfig
 beagleboardx15_defconfig: *defconfig
 beaglebone_defconfig: *defconfig