kconfig: zephyr: use ECDSA with CC310 if CC310 hw is present

This is the preferred signing type with this HW available.
Add 'ECDSA' to the kconfig name to align with the tinycrypt variant.
Remove superfluous checks on select operations.

Signed-off-by: Håkon Øye Amundsen <haakon.amundsen@nordicsemi.no>
diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index a52c7d6..544224f 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -68,6 +68,7 @@
 
 choice
 	prompt "Signature type"
+	default BOOT_SIGNATURE_TYPE_ECDSA_P256 if HAS_HW_NRF_CC310
 	default BOOT_SIGNATURE_TYPE_RSA
 
 config BOOT_SIGNATURE_TYPE_NONE
@@ -92,17 +93,21 @@
 if BOOT_SIGNATURE_TYPE_ECDSA_P256
 choice
 	prompt "Ecdsa implementation"
+	default BOOT_ECDSA_CC310 if HAS_HW_NRF_CC310
 	default BOOT_ECDSA_TINYCRYPT
+
 config BOOT_ECDSA_TINYCRYPT
 	bool "Use tinycrypt"
 	select BOOT_USE_TINYCRYPT
-config BOOT_CC310
+
+config BOOT_ECDSA_CC310
 	bool "Use CC310"
-	select BOOT_USE_NRF_CC310_BL if HAS_HW_NRF_CC310
-	select NRF_CC310_BL if HAS_HW_NRF_CC310
-	select NRFXLIB_CRYPTO if SOC_FAMILY_NRF
+	depends on HAS_HW_NRF_CC310
+	select BOOT_USE_NRF_CC310_BL
+	select NRF_CC310_BL
+	select NRFXLIB_CRYPTO
 	select BOOT_USE_CC310
-endchoice
+endchoice # Ecdsa implementation
 endif
 
 config BOOT_SIGNATURE_TYPE_ED25519