[CRYPTO] salsa20: Add x86-64 assembly version

This is the x86-64 version of the Salsa20 stream cipher algorithm. The
original assembly code came from
<http://cr.yp.to/snuffle/salsa20/amd64-3/salsa20.s>. It has been
reformatted for clarity.

Signed-off-by: Tan Swee Heng <thesweeheng@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/arch/x86/crypto/Makefile b/arch/x86/crypto/Makefile
index 25cc844..09200e1 100644
--- a/arch/x86/crypto/Makefile
+++ b/arch/x86/crypto/Makefile
@@ -8,6 +8,7 @@
 
 obj-$(CONFIG_CRYPTO_AES_X86_64) += aes-x86_64.o
 obj-$(CONFIG_CRYPTO_TWOFISH_X86_64) += twofish-x86_64.o
+obj-$(CONFIG_CRYPTO_SALSA20_X86_64) += salsa20-x86_64.o
 
 aes-i586-y := aes-i586-asm_32.o aes_glue.o
 twofish-i586-y := twofish-i586-asm_32.o twofish_32.o
@@ -15,3 +16,4 @@
 
 aes-x86_64-y := aes-x86_64-asm_64.o aes_glue.o
 twofish-x86_64-y := twofish-x86_64-asm_64.o twofish_64.o
+salsa20-x86_64-y := salsa20-x86_64-asm_64.o salsa20_glue.o