fastboot: allow format on devices with small buffers

Formatting large partitions on devices with small transfer buffers did
not work before since format used a strange path through the code to
send data. It now uses the normal path. Also cleaned up a bit. FS
code now lives in a separate file and the custom path for format is
gone.

Change-Id: If4e01cabc2e250b7c02ca7ce8c268e51d49e1529
diff --git a/fastboot/fastboot.h b/fastboot/fastboot.h
index 976c397..c510a36 100644
--- a/fastboot/fastboot.h
+++ b/fastboot/fastboot.h
@@ -49,7 +49,7 @@
 void fb_queue_flash(const char *ptn, void *data, unsigned sz);
 void fb_queue_flash_sparse(const char *ptn, struct sparse_file *s, unsigned sz);
 void fb_queue_erase(const char *ptn);
-void fb_queue_format(const char *ptn, int skip_if_not_supported);
+void fb_queue_format(const char *ptn, int skip_if_not_supported, unsigned int max_chunk_sz);
 void fb_queue_require(const char *prod, const char *var, int invert,
         unsigned nvalues, const char **value);
 void fb_queue_display(const char *var, const char *prettyname);