CONFIG_RS780_HPET is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

RS780/SBX00 HPET Timer

modulename: hpet.ko

configname: CONFIG_RS780_HPET

Linux Kernel Configuration
└─>RS780/SBX00 HPET Timer
In linux kernel since version 3.10 (release Date: 2013-06-30)  
This option enables the hpet timer of AMD RS780/SBX00.

Note: This driver is doing some dangerous hack. Please only enable
it on RS780E systems.

source code:

depends
CONFIG_BROKEN
CONFIG_MACH_LOONGSON64