smhc: add is cleared functions and several unit test cases

[Placebo27]

Change has_xxx_reset to is_xxx_reset_cleared avoiding potential confusion that DMA_RST, FIFO_RST, SOFT_RST in Global control register and Bit 31 (SMHC_CMD_START, or CMD_LOAD) in Command register are write-1-set, auto-cleared by hardware.

For Global Control Register, add is DMA, FIFO, Software Reset signal cleared by hardware functions and related test cases.
For Command Register, add is command start cleared function and test cases.

Complete the structure read/write function unit tests for Uart Bus Gating Reset, SPI Clock and SPI Bus Gating Registers.