Drop the definition and export of GZFLAGS, which was never referenced
on arm64, and whose last recorded use in the ARM port (on which arm64
was based original) was removed by patch

  commit 5e89d379 [*]
  Author: Russell King <rmk@flint.arm.linux.org.uk>
  Date:   Wed Oct 16 14:32:17 2002 +0100

    [ARM] Convert ARM makefiles to new kbuild (Sam Ravnborg, Kai, rmk)

[*] git commit ID based on Thomas Gleixner's historical GIT repository at
    git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.gitSigned-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20200415123049.25504-1-ardb@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>