Documentation efi-stub.rst: fix arm64 EFI source location

arch/arm64/kernel/efi-entry.S has been moved to
drivers/firmware/efi/libstub/arm64-entry.S by commit
v6.1-rc4-6-g4ef806096bdb and to
drivers/firmware/efi/libstub/arm64.c by commit
v6.2-rc3-6-g617861703830

Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20230904113214.4147021-1-mikko.rapeli@linaro.org>

Documentation/admin-guide/efi-stub.rst

@@ -15,7 +15,7 @@ between architectures is in drivers/firmware/efi/libstub.
 
 For arm64, there is no compressed kernel support, so the Image itself
 masquerades as a PE/COFF image and the EFI stub is linked into the
-kernel. The arm64 EFI stub lives in arch/arm64/kernel/efi-entry.S
+kernel. The arm64 EFI stub lives in drivers/firmware/efi/libstub/arm64.c
 and drivers/firmware/efi/libstub/arm64-stub.c.
 
 By using the EFI boot stub it's possible to boot a Linux kernel