mboxd: Remove flash API compatibility shim

The flash API compatibility was kept to reduce the line noise in the
previous backend patch. Remove the compatibility layer now and convert
the remaining call-sites.

Change-Id: I4b6e54f4463059a7804918add81e7572db7b7c21
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/vpnor/test/write_rw.cpp b/vpnor/test/write_rw.cpp
index 3b742a1..cf9bf7b 100644
--- a/vpnor/test/write_rw.cpp
+++ b/vpnor/test/write_rw.cpp
@@ -48,7 +48,7 @@
 
     /* Test */
     memset(src, 0xbb, sizeof(src));
-    rc = flash_write(ctx, 0x1000, src, sizeof(src));
+    rc = backend_write(&ctx->backend, 0x1000, src, sizeof(src));
     assert(rc == 0);
     fd = open((root.rw() / "TEST1").c_str(), O_RDONLY);
     map = mmap(NULL, sizeof(src), PROT_READ, MAP_SHARED, fd, 0);
@@ -58,31 +58,31 @@
 
     /* Ensure single byte writes function */
     memset(src, 0xcc, sizeof(src));
-    rc = flash_write(ctx, 0x1000, src, sizeof(src));
+    rc = backend_write(&ctx->backend, 0x1000, src, sizeof(src));
     assert(rc == 0);
     rc = memcmp(src, map, sizeof(src));
     assert(rc == 0);
 
     src[0] = 0xff;
-    rc = flash_write(ctx, 0x1000, src, 1);
+    rc = backend_write(&ctx->backend, 0x1000, src, 1);
     assert(rc == 0);
     rc = memcmp(src, map, sizeof(src));
     assert(rc == 0);
 
     src[1] = 0xff;
-    rc = flash_write(ctx, 0x1000 + 1, &src[1], 1);
+    rc = backend_write(&ctx->backend, 0x1000 + 1, &src[1], 1);
     assert(rc == 0);
     rc = memcmp(src, map, sizeof(src));
     assert(rc == 0);
 
     src[2] = 0xff;
-    rc = flash_write(ctx, 0x1000 + 2, &src[2], 1);
+    rc = backend_write(&ctx->backend, 0x1000 + 2, &src[2], 1);
     assert(rc == 0);
     rc = memcmp(src, map, sizeof(src));
     assert(rc == 0);
 
     /* Writes past the end of the partition should fail */
-    rc = flash_write(ctx, 0x1000 + 0xff9, src, sizeof(src));
+    rc = backend_write(&ctx->backend, 0x1000 + 0xff9, src, sizeof(src));
     assert(rc < 0);
 
     /* Check that RW file is unmodified after the bad write */