drm: rp1: rp1-vec: Experimental support for 405 and 819-line TV

Add video mode "544x380i" for obsolete TV System A (405 lines)
Add video mode "848x738i" for obsolete TV System E (819 lines)

Experimental change, in testing. Currently the 819-line mode has
rather non-square pixels (due to the inconvenience of changing
VDAC clock from 108 MHz, and a 1024-column width limit in VEC).
The new modes are monochrome only.

Signed-off-by: Nick Hollinghurst <nick.hollinghurst@raspberrypi.com>