axi_dmac_regmap_request.v: Updating assignment for up_dma_x_length.

[Villyam]

PR Description

• The Lattice Radiant in the default configuration can not automatically infer the array size at concatenation.
• I'm specifying the array size at concatenation to fix the error shown by Lattice Radiant.

PR Type

• Bug fix (change that fixes an issue)
• New feature (change that adds new functionality)
• Breaking change (has dependencies in other repos or will cause CI to fail)

PR Checklist

• I have followed the code style guidelines
• I have performed a self-review of changes
• I have compiled all hdl projects and libraries affected by this PR
• I have tested in hardware affected projects, at least on relevant boards
• I have commented my code, at least hard-to-understand parts
• I have signed off all commits from this PR
• I have updated the documentation (wiki pages, ReadMe files, Copyright etc)
• I have not introduced new Warnings/Critical Warnings on compilation
• I have added new hdl testbenches or updated existing ones

[gastmaier]

The shift assignment is to shift back the value set on line 122-123

  localparam DMAC_DEF_X_LENGTH_DEFAULT = !AUTORUN ? 'h00 :
    AUTORUN_X_LENGTH[DMA_LENGTH_WIDTH-1:DMA_LENGTH_ALIGN];