MIPS: Use generic checksum functions for MIPS R6

The following instructions have been removed from MIPS R6

ulw, ulh, swl, lwr, lwl, swr.

However, all of them are used in the MIPS specific checksum implementation.
As a result of which, we will use the generic checksum on MIPS R6

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index c01e1d4..0a8508b 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1034,6 +1034,9 @@
 config NO_IOPORT_MAP
 	def_bool n
 
+config GENERIC_CSUM
+	bool
+
 config GENERIC_ISA_DMA
 	bool
 	select ZONE_DMA if GENERIC_ISA_DMA_SUPPORT_BROKEN=n
@@ -1312,6 +1315,7 @@
 	select CPU_SUPPORTS_32BIT_KERNEL
 	select CPU_SUPPORTS_HIGHMEM
 	select CPU_SUPPORTS_MSA
+	select GENERIC_CSUM
 	select HAVE_KVM
 	select MIPS_O32_FP64_SUPPORT
 	help
@@ -1363,6 +1367,7 @@
 	select CPU_SUPPORTS_64BIT_KERNEL
 	select CPU_SUPPORTS_HIGHMEM
 	select CPU_SUPPORTS_MSA
+	select GENERIC_CSUM
 	help
 	  Choose this option to build a kernel for release 6 or later of the
 	  MIPS64 architecture.  New MIPS processors, starting with the Warrior