ch32v: Fix up typos in svd

[Grazfather]

Fixed a typo from #528.

Noticed in this warning:

warning(svd): invalid access type: 'read-opnly'
warning(svd): Failed to parse access string 'read-opnly', it must be one of 'read-value', 'write-only', 'read-write', 'writeOnce', or 'read-writeOnce', defaulting to 'read-write'

Fixed the error string to also allow plain 'write', and to specify 'read-only' instead of 'read-value'.

[github-actions]

🔍 Lint Results

Found 1 issue on changed lines in 1 file:

• examples/raspberrypi/rp2xxx/src/net/lwip/net.zig: 1 issue

⚠️ Could not attach inline comments due to an error.