sandybridge: Use calls rather than asm to call to MRC.

sandybridge: Use calls rather than asm to call to MRC.

Using asm as it's done currently is unsafe because caller-saved registers
are not declared as clobbered.

Using real call is nicer.

regparm((1)) ensures that argument is passed in %eax as expected.

Change-Id: I7449182582eaa53d4e473bc834b472edd8ee0d30
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/4675
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>