uhttpd: use P-256 for certs

The uhttpd package takes care of creating self-signed certificates if
px5g is installed. This improves the security of router management as it
encrypts the LuCI connection.

The EC P-256 curve is faster than RSA which which improves the user
experience on embedded devices. EC P-256 is support for as old devices
as Android 4.4.

Signed-off-by: Paul Spooren <mail@aparcar.org>

package/network/services/uhttpd/files/uhttpd.config

@@ -119,13 +119,13 @@ config cert defaults
 	option days		730
 
 	# key type: rsa or ec
-	option key_type		rsa
+	option key_type		ec
 
 	# RSA key size
 	option bits		2048
 
 	# EC curve name
-	# Curve names vary between mbedtls/px5g and openssl
+	# Curve names vary between px5g-{wolfssl,mbedtls} and openssl
 	# P-256 or P-384 are guaranteed to work
 	option ec_curve		P-256