samples: usb: fix flash test subsections in USB MSC sample

Test sections, mass_flash_fatfs and mass_flash_littlefs,
and corresponding Kconfig options are mixed up.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>
diff --git a/samples/subsys/usb/mass/sample.yaml b/samples/subsys/usb/mass/sample.yaml
index 5078fdc..2f3623f 100644
--- a/samples/subsys/usb/mass/sample.yaml
+++ b/samples/subsys/usb/mass/sample.yaml
@@ -34,7 +34,7 @@
     filter: dt_compat_enabled("nordic,qspi-nor")
     extra_configs:
         - CONFIG_LOG_DEFAULT_LEVEL=3
-        - CONFIG_APP_MSC_STORAGE_FLASH_LITTLEFS=y
+        - CONFIG_APP_MSC_STORAGE_FLASH_FATFS=y
     tags: msd usb
     harness: console
     harness_config:
@@ -64,7 +64,7 @@
     filter: dt_compat_enabled("nordic,qspi-nor")
     extra_configs:
         - CONFIG_LOG_DEFAULT_LEVEL=3
-        - CONFIG_APP_MSC_STORAGE_FLASH_FATFS=y
+        - CONFIG_APP_MSC_STORAGE_FLASH_LITTLEFS=y
     tags: msd usb
     harness: console
     harness_config: