board: ti: Add missing common/Kconfig references

Add missing board/ti/common/Kconfig references for the platforms that
missed it. The intent is for the common Kconfig to be usable across TI
reference boards as required.

Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Nishanth Menon <nm@ti.com>

board/ti/omap3evm/Kconfig

@@ -9,4 +9,6 @@ config SYS_VENDOR
 config SYS_CONFIG_NAME
 	default "omap3_evm"
 
+source "board/ti/common/Kconfig"
+
 endif

board/ti/panda/Kconfig

@@ -9,4 +9,6 @@ config SYS_VENDOR
 config SYS_CONFIG_NAME
 	default "omap4_panda"
 
+source "board/ti/common/Kconfig"
+
 endif

board/ti/sdp4430/Kconfig

@@ -12,4 +12,6 @@ config SYS_CONFIG_NAME
 config CMD_BAT
 	bool "Enable board-specific battery command"
 
+source "board/ti/common/Kconfig"
+
 endif