arm/trusted-firmware-m: Fix local source patches application

As TF-M ships patches that it needs applied to mbedcrypto, we apply them as
part of do_patch by using a postfunc. There is an issue when do_patch is
executed after do_deploy_source_date_epoch_setscene and apply_local_patches
tries to apply the patches already applied.

To fix this, make usage of the apply_local_src_patches bbclass.

Change-Id: Ia115b540b37ad3a2cce30e1e0461abd1f5a6ccc1
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>