keymile: common: update to set_env_hex(), fix "pram" radix

keymile: common: update to set_env_hex(), fix "pram" radix

Replace instances of sprintf()/set_env() for setting hexadecimal
values with set_env_hex().

In set_km_env() the "pram" variable was set to an hexadecimal
value, while initr_mem() expects an unsigned decimal, so use
set_env_ulong() instead.

Signed-off-by: Niel Fourie <lusus@denx.de>
Cc: Holger Brunck <holger.brunck@hitachi-powergrids.com>
Cc: Heiko Schocher <hs@denx.de>
Reviewed-by: Stefan Roese <sr@denx.de>
[Rebased]
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>