Staging: dt3155: Cleanup memory mapped i/o access

The macros ReadMReg and WriteMReg are really just private versions of
the kernel's readl and writel functions.  Use the kernel's functions
instead.  And since ioremap returns a (void __iomem *) not a (u8 *),
change all the uses of dt3155_lbase to reflect this.

While here, make dt3155_lbase static since it is only used in the
dt3155_drv.c file.  Also, remove the global variable dt3155_bbase
since it is not used anywhere in the code.

Where is makes sense, create a local 'mmio' variable instead of using
dt3155_lbase[minor] to make the code more readable.

This change also affects the {Read|Write}I2C functions so they are
also modified as needed.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Scott Smedley <ss@aao.gov.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>