env: Fix missed getenv_ulong to env_get_ulong conversion

This seems to have been missed, possibly due to the inability to
enable TI_SECURE_DEVICE on Keystone2 devices previously.

Fixes: bfebc8c965e4 ("env: Rename getenv_hex(), getenv_yesno(), getenv_ulong()")
Signed-off-by: Andrew F. Davis <afd@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
1 file changed