SATA: do not auto-initialize during boot

Rather than have the board code initialize SATA automatically during boot,
make the user manually run "sata init".  This brings the SATA subsystem in
line with common U-Boot policy.

Rather than having a dedicated weak function "is_sata_supported", people
can override sata_initialize() to do their weird board stuff.  Then they
can call the actual __sata_initialize().

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/include/sata.h b/include/sata.h
index 57ee9ac..37573cf 100644
--- a/include/sata.h
+++ b/include/sata.h
@@ -7,5 +7,6 @@
 ulong sata_write(int dev, ulong blknr, ulong blkcnt, const void *buffer);
 
 int sata_initialize(void);
+int __sata_initialize(void);
 
 #endif