arm64: Delete the zero_za macro

zero_za was introduced in commit ca8a4ebc ("arm64/sme: Manually encode
SME instructions") but doesn't appear to have any in kernel user. Drop it.
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20231205160140.1438-1-yuzenghui@huawei.comSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/fpsimdmacros.h

@@ -242,14 +242,6 @@
 		| (\nx << 5)
 .endm
 
-/*
- * Zero the entire ZA array
- *	ZERO ZA
- */
-.macro zero_za
-	.inst 0xc00800ff
-.endm
-
 .macro __for from:req, to:req
 	.if (\from) == (\to)
 		_for__body %\from