videomodes: Relax EDID validation checks for hsync/vsync pulse width

videomodes: Relax EDID validation checks for hsync/vsync pulse width

Current EDID detailed timing parser errors out when either
horizontal or vertical pulse sync width is 0, thus not
allowing a display with EDID listed below work properly.

EDID below works ok within Linux although it warns about
these two fields being 0. Therefore relax the checks a bit
so we can actually use this the screen out of the box.

Of-course, this display itself is somewhat quirky display with
following anti-features:
- HPD pin is not usable
- although resolution is 640x480, only top 240 pixels are visible

$ xxd -p display.edid
00ffffffffffff0005a1e00301000000150f0103800f05780a0f6ea05748
9a2610474f200000010101010101010101010101010101012a08804520e0
0b1020004000953600000018000000fd0034441a2403000a202020202020
0000001000310a20202020202020202020200000001000002a4030701300
782d1100001e006b

$ edid-decode display.edid
EDID version: 1.3
Manufacturer: AMA Model 3e0 Serial Number 1
Digital display
Maximum image size: 15 cm x 5 cm
Gamma: 2.20
RGB color display
First detailed timing is preferred timing
Display x,y Chromaticity:
  Red:   0.6250, 0.3398
  Green: 0.2841, 0.6044
  Blue:  0.1494, 0.0644
  White: 0.2802, 0.3105
Established timings supported:
  640x480@60Hz 4:3 HorFreq: 31469 Hz Clock: 25.175 MHz
Standard timings supported:
Detailed mode: Clock 20.900 MHz, 149 mm x 54 mm
                640  672  672  709 hborder 0
                480  484  484  491 vborder 0
               -hsync -vsync
               VertFreq: 60 Hz, HorFreq: 29478 Hz
Monitor ranges (GTF): 52-68Hz V, 26-36kHz H, max dotclock 30MHz
Dummy block
Dummy block
Checksum: 0x6b (valid)

Signed-off-by: Priit Laes <priit.laes@paf.com>
Signed-off-by: Priit Laes <plaes@plaes.org>