ARCv2: [plat-hsdk]: Save accl reg pair by default

This manifsted as strace segfaulting on HSDK because gcc was targetting
the accumulator registers as GPRs, which kernek was not saving/restoring
by default.

Cc: stable@vger.kernel.org   #4.14+
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/Kconfig

@@ -408,7 +408,7 @@ config ARC_HAS_DIV_REM
 
 config ARC_HAS_ACCL_REGS
 	bool "Reg Pair ACCL:ACCH (FPU and/or MPY > 6)"
-	default n
+	default y
 	help
 	  Depending on the configuration, CPU can contain accumulator reg-pair
 	  (also referred to as r58:r59). These can also be used by gcc as GPR so

arch/arc/plat-hsdk/Kconfig

@@ -7,6 +7,8 @@
 
 menuconfig ARC_SOC_HSDK
 	bool "ARC HS Development Kit SOC"
+	depends on ISA_ARCV2
+	select ARC_HAS_ACCL_REGS
 	select CLK_HSDK
 	select RESET_HSDK
 	select MIGHT_HAVE_PCI