DEVELOPERS, .gitlab-ci.yml: fix typoes in imx6sx-sdb board name

The addition of a new defconfig in commit
459e3320dc234f96b93661bed1a753e477aeab17 ("configs/imx6sx-sdb: Add new
defconfig") introduced changes in the DEVELOPERS file and
.gitlab-ci.yml file that were not matching the defconfig name. This
commit fixes those issues.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

.gitlab-ci.yml

@@ -127,7 +127,7 @@ imx6-sabreauto_defconfig: *defconfig
 imx6-sabresd_defconfig: *defconfig
 imx6-sabresd_qt5_defconfig: *defconfig
 imx6slevk_defconfig: *defconfig
-imx6sxsdb_defconfig: *defconfig
+imx6sx-sdb_defconfig: *defconfig
 imx6ulevk_defconfig: *defconfig
 imx6ulpico_defconfig: *defconfig
 imx7dpico_defconfig: *defconfig

DEVELOPERS

@@ -581,7 +581,7 @@ F:	board/warp7/
 F:	configs/freescale_imx*
 F:	configs/imx6-sabresd*
 F:	configs/imx6slevk_defconfig
-F:	configs/imx6sxsdb_defconfig
+F:	configs/imx6sx-sdb_defconfig
 F:	configs/imx6ulevk_defconfig
 F:	configs/imx6ulpico_defconfig
 F:	configs/mx6cubox_defconfig