cmd: bcb: Fix bcb compilation when CONFIG_CMD_BCB=n

commit dfeb4f0d7935 ("cmd: bcb: extend BCB C API to allow read/write the fields")
introduced the bcb_get() function.

When CONFIG_CMD_BCB=n, that function is stubbed.
The stubbed function has a wrong prototype: value_size arg is missing.

Add the missing argument to fix build when CONFIG_CMD_BCB=n.

Fixes: dfeb4f0d7935 ("cmd: bcb: extend BCB C API to allow read/write the fields")
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Reviewed-by: Guillaume La Roque <glaroque@baylibre.com>
Reviewed-by: Dmitrii Merkurev <dimorinny@google.com>
Reviewed-by: Julien Masson <jmasson@baylibre.com>
diff --git a/include/bcb.h b/include/bcb.h
index 1941d8c..a56b547 100644
--- a/include/bcb.h
+++ b/include/bcb.h
@@ -58,7 +58,8 @@
 	return -EOPNOTSUPP;
 }
 
-static inline int bcb_get(enum bcb_field field, char *value_out)
+static inline int bcb_get(enum bcb_field field,
+			  char *value_out, size_t value_size)
 {
 	return -EOPNOTSUPP;
 }