Fix defines needed to enable command sha1sum

Documented is CONFIG_CMD_SHA1, through confusion in the source
CONFIG_CMD_SHA1 and CONFIG_CMD_SHA1SUM has to be used to enable
sha1sum.

Fix both, the documentation and the source, so that only
CONFIG_CMD_SHA1SUM is needed to enable the command sha1sum.

Signed-off-by: Alexander Holler <holler@ahsoftware.de>

README

diff --git a/README b/README
index 8e1a9ff..755d17c 100644
--- a/README
+++ b/README
@@ -675,7 +675,7 @@
 					  (requires CONFIG_CMD_I2C)
 		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
 					  (4xx only)
-		CONFIG_CMD_SHA1		  print sha1 memory digest
+		CONFIG_CMD_SHA1SUM	  print sha1 memory digest
 					  (requires CONFIG_CMD_MEMORY)
 		CONFIG_CMD_SOURCE	  "source" command Support
 		CONFIG_CMD_SPI		* SPI serial bus support

common/cmd_mem.c

diff --git a/common/cmd_mem.c b/common/cmd_mem.c
index f03233c..ccf420a 100644
--- a/common/cmd_mem.c
+++ b/common/cmd_mem.c
@@ -1184,7 +1184,7 @@
 }
 #endif
 
-#ifdef CONFIG_CMD_SHA1
+#ifdef CONFIG_CMD_SHA1SUM
 int do_sha1sum(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	unsigned long addr, len;
@@ -1343,7 +1343,7 @@
 	"compute SHA1 message digest",
 	"address count"
 );
-#endif /* CONFIG_CMD_SHA1 */
+#endif /* CONFIG_CMD_SHA1SUM */
 
 #ifdef CONFIG_CMD_UNZIP
 U_BOOT_CMD(