[top_earlgrey] Remove outdated comments
[top_earlgrey] Remove outdated comments

The RAM and ROM primitives will provide ASIC-specific implementations,
which are transparent to the toplevel file. Remove the TODO comments
which indicate something else.

Signed-off-by: Philipp Wagner <5a4b10454c30419e54a1570be358a516ff84bb63@lowrisc.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan