arm64: Avoid cache flushing in flush_dcache_page()

arm64: Avoid cache flushing in flush_dcache_page()

commit b5b6c9e9149d8a7c3f1d7b9d0c046c6184e1dd17 upstream.

The flush_dcache_page() function is called when the kernel modified a
page cache page. Since the D-cache on AArch64 does not have aliases
this function can simply mark the page as dirty for later flushing via
set_pte_at()/__sync_icache_dcache() if the page is executable (to ensure
the I-D cache coherency).

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Will Deacon <will.deacon@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>