microblaze: Enable asm optimization only for HW with barrel-shifter

Asm code uses barrel-shifter instruction that's why we have
to protect cases when HW don't have it.

Reported-by: John Linn <john.linn@xilinx.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/platform/Kconfig.platform

@@ -53,7 +53,7 @@ config OPT_LIB_FUNCTION
 
 config OPT_LIB_ASM
 	bool "Optimalized lib function ASM"
-	depends on OPT_LIB_FUNCTION
+	depends on OPT_LIB_FUNCTION && (XILINX_MICROBLAZE0_USE_BARREL = 1)
 	default n
 	help
 	  Allows turn on optimalized library function (memcpy and memmove).