[MIPS] AP/SP requires shadow registers, auto enable support.

Noticed by Chris Dearman (chris@mips.com).
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -1392,6 +1392,7 @@ config MIPS_VPE_LOADER
 	depends on SYS_SUPPORTS_MULTITHREADING
 	select CPU_MIPSR2_IRQ_VI
 	select CPU_MIPSR2_IRQ_EI
+	select CPU_MIPSR2_SRS
 	select MIPS_MT
 	help
 	  Includes a loader for loading an elf relocatable object