zephyr: boards: set BOOT_MAX_IMG_SECTORS value for rd_rw612_bga

MX25UM flash on rd_rw612_bga is very large (8MB), so we must increase
the number of max sectors when targeting this board with MCUboot

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>
diff --git a/boot/zephyr/boards/rd_rw612_bga.conf b/boot/zephyr/boards/rd_rw612_bga.conf
new file mode 100644
index 0000000..3a751f2
--- /dev/null
+++ b/boot/zephyr/boards/rd_rw612_bga.conf
@@ -0,0 +1,4 @@
+# Copyright 2024 NXP
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_BOOT_MAX_IMG_SECTORS=1024