Regression: `pc.js ibm5150 --boot=none` no longer boots ROM BASIC

[skissane]

According to the blog post https://www.pcjs.org/blog/2023/07/15/ running pc.js ibm5150 --boot=none is supposed to boot to ROM BASIC.

However, this was broken by commit f70d366

If you do:

git checkout f70d36616fe26ba9a3924f11045d19eae9577111~1
./pc.js ibm5150 --boot=none

it will indeed boot ROM BASIC

However, if instead you do:

git checkout f70d36616fe26ba9a3924f11045d19eae9577111
./pc.js ibm5150 --boot=none

it will boot PC DOS instead. The same remains true with latest master branch.

I have a PR which fixes this, see #116