Kconfig: Introduce CONFIG_SYS_HAS_SRAM

In order to be able to replace "#ifdef CONFIG_SYS_SRAM_BASE" sequences
with the IS_ENABLED() equivalent, introduce a new boolean Kconfig option
that signals whether the platform has SRAM support.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
diff --git a/Kconfig b/Kconfig
index 1c408b6..54b3680 100644
--- a/Kconfig
+++ b/Kconfig
@@ -379,6 +379,17 @@
 	  by the UEFI sub-system. On some boards initrd_high is calculated as
 	  base stack pointer minus this stack size.
 
+config SYS_HAS_SRAM
+	bool
+	default y if TARGET_PIC32MZDASK
+	default y if TARGET_DEVKIT8000
+	default y if TARGET_TRICORDER
+	default n
+	help
+	  Enable this to allow support for the on board SRAM.
+	  SRAM base address is controlled by CONFIG_SYS_SRAM_BASE.
+	  SRAM size is controlled by CONFIG_SYS_SRAM_SIZE.
+
 endmenu		# General setup
 
 menu "Boot images"