complier.h: add __always_inline and use it in code base

Add a __always_inline macro that wraps __attribute__((always_inline))
and replace current users with the macro, excluding files under
src/vendorcode.

Change-Id: Ic57e474c1d2ca7cc0405ac677869f78a28d3e529
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/28587
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@google.com>

src/cpu/x86/smm/smihandler.c

@@ -60,7 +60,7 @@ void smi_release_lock(void)
 }
 
 #define LAPIC_ID 0xfee00020
-static inline __attribute__((always_inline)) unsigned long nodeid(void)
+static __always_inline unsigned long nodeid(void)
 {
 	return (*((volatile unsigned long *)(LAPIC_ID)) >> 24);
 }