psa: Pick up code from MBED_PSA_SRV

Make single Armv7-M PSA targets pick up files under TARGET_MBED_PSA_SRV.
We'll be moving the Mbed implementation of PSA to TARGET_MBED_PSA_SRV
folders soon.

Targets (dual-core and Armv8-M) that expect to use TF-M for their PSA
implementation also have MBED_PSA_SRV labels added to them so that they
continue working with the Mbed PSA implementation for the time being.

targets/targets.json

@@ -765,7 +765,8 @@
             "KPSDK_CODE",
             "MCU_K64F",
             "Freescale_EMAC",
-            "PSA"
+            "PSA",
+            "MBED_PSA_SRV"
         ],
         "is_disk_virtual": true,
         "macros": [
@@ -1022,7 +1023,8 @@
             "KSDK2_MCUS",
             "FRDM",
             "Freescale_EMAC",
-            "PSA"
+            "PSA",
+            "MBED_PSA_SRV"
         ],
         "is_disk_virtual": true,
         "macros": [
@@ -1983,7 +1985,8 @@
         "extra_labels_add": [
             "STM32F4",
             "STM32F429xI",
-            "PSA"
+            "PSA",
+            "MBED_PSA_SRV"
         ],
         "macros_add": [
             "STM32F429xx"
@@ -4691,6 +4694,7 @@
         "extra_labels_add": [
             "MUSCA_A1_NS",
             "PSA",
+            "MBED_PSA_SRV",
             "TFM"
         ],
         "post_binary_hook": {
@@ -4748,6 +4752,7 @@
         "extra_labels_add": [
             "MUSCA_B1_NS",
             "PSA",
+            "MBED_PSA_SRV",
             "TFM"
         ],
         "post_binary_hook": {
@@ -6273,7 +6278,8 @@
         "public": false,
         "extra_labels": [
             "ARM_FM",
-            "PSA"
+            "PSA",
+            "MBED_PSA_SRV"
         ]
     },
     "FVP_MPS2": {
@@ -7306,7 +7312,8 @@
             "GD32F4XX",
             "GD32F450ZI",
             "GD_EMAC",
-            "PSA"
+            "PSA",
+            "MBED_PSA_SRV"
         ],
         "device_has_add": [
             "RTC",