palmas: use palmas_i2c_[read|write]_u8

commit 21144298 (power: twl6035: add palmas PMIC support)
introduced twl6035_i2c_[read|write]_u8
Then, commit dd23e59d (omap5: pbias ldo9 turn on)
introduced palmas_[read|write]_u8 for precisely the same access
function. TWL6035 belongs to the palmas family, so instead of having
an twl6035 API, we could use an generic palmas API instead.

To stay consistent with the function naming of twl4030,6030 accessors,
we use palmas_i2c_[read|write]_u8

Cc: Balaji T K <balajitk@ti.com>
Cc: Sricharan R <r.sricharan@ti.com>
Reported-by: Ruchika Kharwar <ruchika@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>