xen/netback: do some code cleanup

stable inclusion
from stable-v5.10.159
commit 3eecd2bc10e0af4fe8d913ff5a57927abc4f81bb
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7NTXH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3eecd2bc10e0af4fe8d913ff5a57927abc4f81bb



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[ Upstream commit 5834e72e ]

Remove some unused macros and functions, make local functions static.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/20220608043726.9380-1-jgross@suse.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 74e7e1ef ("xen/netback: don't call kfree_skb() with interrupts disabled")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>

Conflicts:
	drivers/net/xen-netback/common.h