Replace 'Reg_array' in 'Genode::Mmio' by 'Register_array' and 'Subreg'
in 'Genode::Register', 'Genode::Mmio::Register'and
'Genode::Mmio::Register_array' by 'Bitfield'.
Update and beautify comments in the according headers and test programs.
'Reg_array' contains items whose width can be the width of the register
storage type at a max. Nethertheless they can be smaller and iterate all
subregs that are covered by the item width. The array uses as much
successive instances of its storage type as needed.
The test 'run/util_mmio' also tests these new features heavily.
The run script 'run/util_mmio.run' runs a test over basic
functionalities of 'Mmio::Register' and 'Mmio::Register::Subreg'. The
test covers the functions 'read' and 'bits', 'set', 'clear' and 'get'.
Inline function in 'Mmio::Register::Subreg' whose definition otherwise
looks ugly.
To accommodate CPU registers, which have a structured layout but don't
depend on a region base address, this patch introduces the generic
'Genode::Register' and 'Genode::Subreg' to 'register.h'.
'Mmio::Register' and 'Mmio::Subreg' inherit from them.
The MMIO access framework consists of an abstraction for a contiguous
MMIO area with a base address set dynamically. Within this class 'Mmio'
are declarations for 'Register' and 'Subreg'. These two can be
parameterized statically via template parameters to create arbitrary
MMIO structures.
Whereas 'Register' relies to a POD like subregion of 'Mmio', 'Subreg'
relies to a MMIO region within a specific 'Register' and therefore is
smaller or equal then the storage type of its superior 'Register'.
Furthermore with 'Reg_array' and 'Subreg_array', there exists the
possibility to handle arrays of uniform contiguous registers or subregs
by index. 'Subreg_array' therefore abstracts from the width boundary of
its superior 'Register' and handles a steady distance between its
members in addition. Both also check array size limits.
Related to issue #69.
