manifest: tf-m: add support for RSA signatures with 2048-bit keys

Update TF-M reference to include a couple of commits which are
useful to properly size the stack & heap memory for Mbed TLS
in order to handle RSA signatures with 2048-bits (previously
only 1024-bits were possible).

Signed-off-by: Valerio Setti <vsetti@baylibre.com>