[rom_ctrl,doc] Remove dotted box from block diagram

When we originally specced this module out, it looked like it might be
a good idea to implement the "scrambled ROM" with a primitive. As it
turns out, this was pretty simple and it's probably easier to just
inline it. Update the block diagram to match.

Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
diff --git a/hw/ip/rom_ctrl/doc/rom_ctrl_blockdiag.svg b/hw/ip/rom_ctrl/doc/rom_ctrl_blockdiag.svg
index fd6d784..30fdf75 100644
--- a/hw/ip/rom_ctrl/doc/rom_ctrl_blockdiag.svg
+++ b/hw/ip/rom_ctrl/doc/rom_ctrl_blockdiag.svg
@@ -721,8 +721,8 @@
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      inkscape:zoom="0.89639071"
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@@ -754,11 +754,6 @@
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@@ -1621,33 +1616,6 @@
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      xml:space="preserve"
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-       id="tspan3117">The current plan is to implement</tspan><tspan
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-       id="tspan3149">for sram_ctrl.</tspan></text>
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