rand() by default does increment of 1, randomizing more

Random number generation in case of IAR 8, requires TLS support.
Thread local storage is not part of Mbed OS, test is updated to have random
numbers sparse, but in future random number creation should be moved to main
thread, or use some other logic for randomization instead of rand() call.

Author: Deepika

components/storage/blockdevice/COMPONENT_SPIF/TESTS/block_device/spif/main.cpp

@@ -49,8 +49,9 @@ void basic_erase_program_read_test(SPIFBlockDevice &block_device, bd_size_t bloc
     _mutex->lock();
 
     // Make sure block address per each test is unique
-    static unsigned block_seed = 1;
-    srand(block_seed++);
+    static unsigned block_seed = SPIF_TEST_NUM_OF_THREADS;
+    srand(block_seed);
+    block_seed += 2;
 
     // Find a random block
     bd_addr_t block = (rand() * block_size) % block_device.size();

features/storage/TESTS/blockdevice/general_block_device/main.cpp

@@ -189,8 +189,9 @@ void basic_erase_program_read_test(BlockDevice *block_device, bd_size_t block_si
     _mutex->lock();
 
     // Make sure block address per each test is unique
-    static unsigned block_seed = 1;
-    srand(block_seed++);
+    static unsigned block_seed = TEST_NUM_OF_THREADS;
+    srand(block_seed);
+    block_seed += 2;
 
     // Find a random block
     bd_addr_t block = (rand() * block_size) % (block_device->size());