please update package ppp from latest openwrt

[lhc1993]

Is your feature request related to a problem? Please describe.

The hash value of the ppp package has not been updated, but it has been updated on OpenWRT. Please synchronize it
Describe the solution you'd like

Update the PKG_MIRROR_HASH value in the PPP makefile to 381668ce1547afeaf599f08ae37935bfd3d5841747c62bca5a870c11e3e9bedb

Describe alternatives you've considered

Additional context

[Ysurac]

I'm not forking ppp package, so OpenWRT package is used on a fixed commit. I will update OpenWRT fixed commit.