s5k3l6xx: Update digital gain control range

S5K3L6XX_Application Note_REV0.20 specifies digital gain to be
in range of 1.0x (0x100) to 3.0x (0x300).
2 jobs for dgain in 67 minutes and 45 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #352813
librem5
build:aarch64

00:37:42

passed #352814
librem5:arm64
build:deb

01:07:44