Fix ldscript for bootblock .rom section

Fix ldscript for bootblock .rom section

Allocation size for the section was miscalculated, so the section
did not honour its upper-bound address.

Also align the section start to 4 bytes, so it starts with code
instead of pad bytes.

Change-Id: Ic2a43981836a0873b50abecfcad2def7b6586a5d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/453
Tested-by: build bot (Jenkins)
Reviewed-by: Alec Ari <neotheuser@ymail.com>
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>