TI: bootstd: android: fix dtbo implementation
When DTBO support was added we miss to add in kernel commandline: androidboot.dtbo_idx=XX
Create a function to read adtbo_idx variable and if we find a value add it in kernel command line.
Fixes: 1c6cf852 ("TI: bootstd: android: Implement DTBO support") Signed-off-by: Guillaume La Roque glaroque@baylibre.com