Exynos: uart: s5p: enabling the uart tx/rx fifo

Exynos: uart: s5p: enabling the uart tx/rx fifo

This patch enables the uart tx/rx fifo. Now that fifo is enabled,
the uart read/write functions are modfied to check the UFSTAT register
for fifo status instead of UTRSTAT (as required with fifo's enabled).
Tested by booting linux kernel. Before enabling tx/rx fifo
"Uncompressing linux" message is garbled and after enabling it is proper.

Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Akshay Saraswat <akshay.s@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>