Adopted erase_size config changes in block devices and test runners

This ended up needing a bit of API rework since littlefs no longer needs
to know the actual erase_count. We can no longer rely on lfs_config to
contain all the information necessary to configure the block devices.

Changing the lfs_bd_config structs to be required is probably a good
idea anyways as it moves us more towards separating the bds from
littlefs, though we can't quite get rid of the lfs_config parameter
because of the block-device API in lfs_config. Eventually it would be
nice to get rid of it, but that would require API breakage.

bd/lfs_rambd.h

@@ -26,8 +26,20 @@ extern "C"
 #endif
 #endif
 
-// rambd config (optional)
+// rambd config
 struct lfs_rambd_config {
+    // Minimum size of a read operation in bytes.
+    lfs_size_t read_size;
+
+    // Minimum size of a program operation in bytes.
+    lfs_size_t prog_size;
+
+    // Size of an erase operation in bytes.
+    lfs_size_t erase_size;
+
+    // Number of erase blocks on the device.
+    lfs_size_t erase_count;
+
     // Optional statically allocated buffer for the block device.
     void *buffer;
 };
@@ -39,9 +51,8 @@ typedef struct lfs_rambd {
 } lfs_rambd_t;
 
 
-// Create a RAM block device using the geometry in lfs_config
-int lfs_rambd_create(const struct lfs_config *cfg);
-int lfs_rambd_createcfg(const struct lfs_config *cfg,
+// Create a RAM block device
+int lfs_rambd_create(const struct lfs_config *cfg,
         const struct lfs_rambd_config *bdcfg);
 
 // Clean up memory associated with block device