arm64: Fix comments to refer to correct function __flush_icache_range

arm64: Fix comments to refer to correct function __flush_icache_range

Many comments refer to the function flush_icache_range, where the
intent is in fact __flush_icache_range. Fix these comments to
refer to the intended function.

That's probably due to commit 3b8c9f1cdfc506e9 ("arm64: IPI each
CPU after invalidating the I-cache for kernel mappings"), which
renamed flush_icache_range() to __flush_icache_range() and added
a wrapper.

No functional change intended.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210524083001.2586635-10-tabba@google.com
Signed-off-by: Will Deacon <will@kernel.org>