common/cmd_nvedit.c: Fix size calculation in do_env_import()

do_env_import() missed the final '\0' terminator when calculating the
size of an environment data block.  This led to an erroneous 'bad CRC,
import failed' message for a checksum protected environment (-c.)
Signed-off-by: NHorst Kronstorfer <hkronsto@frequentis.com>

common/cmd_nvedit.c

@@ -868,7 +868,7 @@ static int do_env_import(cmd_tbl_t *cmdtp, int flag,
 			printf("## Warning: Input data exceeds %d bytes"
 				" - truncated\n", MAX_ENV_SIZE);
 		}
-		++size;
+		size += 2;
 		printf("## Info: input data size = %zu = 0x%zX\n", size, size);
 	}