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/soc/nvidia/tegra124/lp0/tegra_lp0_resume.c

@@ -264,8 +264,7 @@ static uint32_t *sysctr_cntfid0_ptr = (void *)(SYSCTR_CTLR_BASE + 0x20);
 
 /* Utility functions. */
 
-static inline void __attribute__((always_inline))
-		   __noreturn halt(void)
+static __always_inline void __noreturn halt(void)
 {
 	for (;;);
 }

src/soc/nvidia/tegra210/lp0/tegra_lp0_resume.c

@@ -428,8 +428,7 @@ enum {
 
 /* Utility functions. */
 
-static inline void __attribute__((always_inline))
-		   __noreturn halt(void)
+static __always_inline void __noreturn halt(void)
 {
 	for (;;);
 }