AMD: Drop six copies of wrmsr_amd and rdmsr_amd

Based on comments in cpu/x86/msr.h for wrmsr/rdmsr, and for symmetry,
I have added __attribute__((always_inline)) for these.

Change-Id: Ia0a34c15241f9fbc8c78763386028ddcbe6690b1
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/2898
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Marc Jones <marc.jones@se-eng.com>

src/include/cpu/amd/amdfam12.h

@@ -33,9 +33,6 @@
 #define CPU_ID_FEATURES_MSR		0xC0011004
 #define CPU_ID_EXT_FEATURES_MSR	0xC0011005
 
-msr_t rdmsr_amd(u32 index);
-void wrmsr_amd(u32 index, msr_t msr);
-
 //#if defined(__GNUC__)
 //// it can be used to get unitid and coreid it running only
 //struct node_core_id get_node_core_id(u32 nb_cfg_54);