power: pmic.h: Drop include <spi.h>

power: pmic.h: Drop include <spi.h>

include/power/pmic.h never used any generic spi code
from include/spi.h, but this has been added in below commit.
"dm: pmic: add implementation of driver model pmic uclass"
(sha1: 4d9057e82be11a862db411c4867e859fe0d4ca2a)

Adding functionalities in include/spi.h will trigger a build
issue as this been added used in include/power/pmic.h

Build issue on trats2 with adding BIT macro on spi.h:
----------------------------------------------------
  CC      lib/asm-offsets.s
In file included from include/power/pmic.h:15:0,
                 from include/power/max77686_pmic.h:11,
                 from include/configs/trats2.h:212,
                 from include/config.h:5,
                 from include/common.h:18,
                 from lib/asm-offsets.c:15:
include/spi.h: In function 'spi_w8r8':
include/spi.h:327:2: warning: implicit declaration of function 'BIT' [-Wimplicit-function-declaration]

Cc: Simon Glass <sjg@chromium.org>
Cc: Przemyslaw Marczak <p.marczak@samsung.com>
Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Jagan Teki <jteki@openedev.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Simon Glass <sjg@chromium.org>