CI: move stm32mp157c-dk2 to be alphabetical

Trivial change to move stm32mp157c-dk2 to its alphabetical location.
This is relevant because it aligns the file to match the order on the
gilab pipeline entry.

Signed-off-by: Jon Mason <jon.mason@arm.com>
Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>

.gitlab-ci.yml

@@ -77,9 +77,6 @@ intel-x86-64:
 nrf52840dk-nrf52840:
   extends: .build
 
-stm32mp157c-dk2:
-  extends: .build
-
 qemu-cortex-m3/testimage:
   extends: .build
 
@@ -88,3 +85,6 @@ qemu-nios2:
 
 qemu-x86/testimage:
   extends: .build
+
+stm32mp157c-dk2:
+  extends: .build