esp32/Makefile: Define and use ESPCOMP variable.
esp32/Makefile: Define and use ESPCOMP variable.

Almost all parts of the ESP IDF live in the components/ subdirectory so
having a variable for this dir makes the Makefile more concise.

MrSurly/micropython-esp32,SHA2017-badge/micropython-esp32,micropython/micropython-esp32,micropython/micropython-esp32,MrSurly/micropython-esp32,MrSurly/micropython-esp32,Peetz0r/micropython-esp32,SHA2017-badge/micropython-esp32,MrSurly/micropython-esp32,Peetz0r/micropython-esp32,SHA2017-badge/micropython-esp32,micropython/micropython-esp32,Peetz0r/micropython-esp32,SHA2017-badge/micropython-esp32,SHA2017-badge/micropython-esp32,MrSurly/micropython-esp32,micropython/micropython-esp32,Peetz0r/micropython-esp32,micropython/micropython-esp32,Peetz0r/micropython-esp32