This changes the prefixes of the symbols generated from USEMODULE and
USEPKG variables. The changes are as follow:
KCONFIG_MODULE_ => KCONFIG_USEMODULE_
KCONFIG_PKG_ => KCONFIG_USEPKG_
MODULE_ => USEMODULE_
PKG_ => USEPKG_
First, every read function converts the void pointer into a const bmx055_t
Second, it is cleaner (more obvious) to pass phydat_t.val[3] instead of
type casting to int16_t* and relying that .val[3] is the first struct
member of phydat_t.
