Greentea: Fix storage sizes for SecureStore tests.

Previously Greentea tests was not initialising its storage
before asking for bd->get_program_size(), causing FlashBlockDevice to
return zero. This caused both TDBStorage's to use zero for both
parameter to SlicingBlockDevice(bd, 0, 0), effetivaly both then
used same addresses for slice. This caused SecureStore tests
to fail, because writes to internal RBP storage overwrote keys
from external storage.

Fine-tune TDBStore sizes, so that all tests can fit into storage.

features/storage/TESTS/kvstore/general_tests_phase_1/main.cpp

@@ -28,6 +28,7 @@
 #include "unity/unity.h"
 #include "utest/utest.h"
 #include "FileSystemStore.h"
+#include "features/storage/internal/utils.h"
 
 using namespace utest::v1;
 using namespace mbed;
@@ -74,7 +75,7 @@ static const int heap_alloc_threshold_size = 4096;
 static void kvstore_init()
 {
     int res;
-    size_t erase_size, ul_bd_size, rbp_bd_size;
+    size_t program_size, erase_size, ul_bd_size, rbp_bd_size;
     BlockDevice *sec_bd;
 
     res = bd->init();
@@ -109,10 +110,17 @@ static void kvstore_init()
             flash_bd = new FlashSimBlockDevice(bd);
             sec_bd = flash_bd;
         }
+        res = sec_bd->init();
+        TEST_ASSERT_EQUAL_ERROR_CODE(MBED_SUCCESS, res);
+
+        program_size  = sec_bd->get_program_size();
+        erase_size = sec_bd->get_erase_size();
+        // We must be able to hold at least 10 small keys (20 program sectors) and master record + internal data
+        ul_bd_size  = align_up(program_size * 40, erase_size);
+        rbp_bd_size = align_up(program_size * 40, erase_size);
 
-        erase_size  = sec_bd->get_erase_size();
-        ul_bd_size  = erase_size * 4;
-        rbp_bd_size = erase_size * 2;
+        res = sec_bd->deinit();
+        TEST_ASSERT_EQUAL_ERROR_CODE(MBED_SUCCESS, res);
 
         ul_bd = new SlicingBlockDevice(sec_bd, 0, ul_bd_size);
         rbp_bd = new SlicingBlockDevice(sec_bd, ul_bd_size, ul_bd_size + rbp_bd_size);
@@ -424,14 +432,14 @@ static void set_several_key_value_sizes()
 
     name[6] = 0;
 
-    for (i = 0; i < 26; i++) {
+    for (i = 0; i < 5; i++) {
         c = i + 'a';
         name[5] = c;
         res = kvstore->set(name, name, sizeof(name), 0);
         TEST_ASSERT_EQUAL_ERROR_CODE(MBED_SUCCESS, res);
     }
 
-    for (i = 0; i < 26; i++) {
+    for (i = 0; i < 5; i++) {
         c = i + 'a';
         name[5] = c;
         res = kvstore->get(name, buffer, sizeof(buffer), &actual_size, 0);