acpidump: Extend the decoding of entries in the EINJ and ERST tables

• Decode the Action, Instruction, and Flags fields for these tables

• Omit the Flags field if it is zero

• Omit the Value field for instrunctions that do not use it

Reviewed by: imp
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D54308

(cherry picked from commit 6b2e4da4430029b16591c64aaef78bcd1644cedc)