MIPS: ralink: add missing symbol for RALINK_ILL_ACC

A driver was added in commit 5433acd8 ("MIPS: ralink: add illegal access
driver") without the Kconfig section being added. Fix this by adding the symbol
to the Kconfig file.
Signed-off-by: John Crispin <blogic@openwrt.org>
Reported-by: Paul Bolle <pebolle@tiscali.nl>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9299/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/ralink/Kconfig

@@ -7,6 +7,11 @@ config CLKEVT_RT3352
 	select CLKSRC_OF
 	select CLKSRC_MMIO
 
+config RALINK_ILL_ACC
+	bool
+	depends on SOC_RT305X
+	default y
+
 choice
 	prompt "Ralink SoC selection"
 	default SOC_RT305X