arm64: vdso: remove two .altinstructions related symbols

The two symbols __alt_instructions and __alt_instructions_end are not
used, since the vDSO patching code looks for the '.altinstructions' ELF
section directly.

Remove the unused linker symbols.

Fixes: 4e3bca8f ("arm64: alternative: patch alternatives in the vDSO")
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20230726173619.3732-1-jszhang@kernel.org


Signed-off-by: Will Deacon <will@kernel.org>