arm64: assembler: remove user_alt

user_alt isn't being used anymore. It's also simpler and clearer
to directly use alternative_insn and _cond_extable in-line when
needed.

Reported-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/linux-arm-kernel/20210520125735.GF17233@C02TD0UTHF1T.local/
Signed-off-by: Fuad Tabba <tabba@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210524083001.2586635-8-tabba@google.com
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/alternative-macros.h

@@ -197,11 +197,6 @@ alternative_endif
 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...)	\
 	alternative_insn insn1, insn2, cap, IS_ENABLED(cfg)
 
-.macro user_alt, label, oldinstr, newinstr, cond
-9999:	alternative_insn "\oldinstr", "\newinstr", \cond
-	_asm_extable 9999b, \label
-.endm
-
 #endif  /*  __ASSEMBLY__  */
 
 /*