arm: k3: Add regex/gsub command handling

The 'gsub' setexpr sub command is using when creating the FIT image
configuration string on K3 devices. Enable this for K3.

Signed-off-by: Andrew Davis <afd@ti.com>
Signed-off-by: Manorit Chawdhry <m-chawdhry@ti.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b3115b0..3045698 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -798,6 +798,7 @@
 	select SPL
 	select SUPPORT_SPL
 	select FIT
+	select REGEX
 
 config ARCH_OMAP2PLUS
 	bool "TI OMAP2+"