Current minimum required version of binutils is 2.23,
which supports CRC32 instruction mnemonic.

Replace the byte-wise specification of CRC32 with this proper mnemonic.
The compiler is now able to pass memory operand to the instruction,
so there is no need for a temporary register anymore.

Some examples of the improvement:

 12a:	48 8b 08             	mov    (%rax),%rcx
 12d:	f2 48 0f 38 f1 f1    	crc32q %rcx,%rsi
 133:	48 83 c0 08          	add    $0x8,%rax
 137:	48 39 d0             	cmp    %rdx,%rax
 13a:	75 ee                	jne    12a <crc32c_intel_update+0x1a>

to:

 125:	f2 48 0f 38 f1 06    	crc32q (%rsi),%rax
 12b:	48 83 c6 08          	add    $0x8,%rsi
 12f:	48 39 d6             	cmp    %rdx,%rsi
 132:	75 f1                	jne    125 <crc32c_intel_update+0x15>

and:

 146:	0f b6 08             	movzbl (%rax),%ecx
 149:	f2 0f 38 f0 f1       	crc32b %cl,%esi
 14e:	48 83 c0 01          	add    $0x1,%rax
 152:	48 39 d0             	cmp    %rdx,%rax
 155:	75 ef                	jne    146 <crc32c_intel_update+0x36>

to:

 13b:	f2 0f 38 f0 02       	crc32b (%rdx),%eax
 140:	48 83 c2 01          	add    $0x1,%rdx
 144:	48 39 ca             	cmp    %rcx,%rdx
 147:	75 f2                	jne    13b <crc32c_intel_update+0x2b>

As the compiler has some more freedom w.r.t. register allocation,
there is also a couple of reg-reg moves removed.

There are no hidden states for CRC32 insn, so there is no need to mark
assembly as volatile.

v2: Introduce CRC32_INST define.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: "David S. Miller" <davem@davemloft.net>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
CC: Borislav Petkov <bp@alien8.de>
CC: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>