siemens: eeprom: simplify setup & read

Since we have boards using the driver model or not for i2c, use abstraction
function to probe the i2c, check the EEPROM and read from EEPROM.

Signed-off-by: Enrico Leto <enrico.leto@siemens.com>
diff --git a/board/siemens/pxm2/board.c b/board/siemens/pxm2/board.c
index 9e85d9b..16b0d3d 100644
--- a/board/siemens/pxm2/board.c
+++ b/board/siemens/pxm2/board.c
@@ -161,7 +161,6 @@
 		printf("voltage update failed\n");
 	}
 }
-#endif /* if def CONFIG_SPL_BUILD */
 
 int read_eeprom(void)
 {
@@ -169,6 +168,7 @@
 
 	return 0;
 }
+#endif /* if def CONFIG_SPL_BUILD */
 
 #if (defined(CONFIG_DRIVER_TI_CPSW) && !defined(CONFIG_SPL_BUILD)) || \
 	(defined(CONFIG_SPL_ETH) && defined(CONFIG_SPL_BUILD))